Method and apparatus for forming tow-based absorbent structures with a single casing sheet

ABSTRACT

An apparatus and method for forming tow-based absorbent structures having a single casing sheet are disclosed. The apparatus has a tow supply mechanism for providing tow material, a particulate matter supply mechanism for providing particulate matter, and a casing sheet supply mechanism for providing casing sheet material. The apparatus also has a vacuum draw roll having a foraminous center surface that has a width defined by a first edge and a second edge and is rotatable about a first axis. The vacuum draw roll is positioned to receive the tow material, the particulate matter and the casing sheet material to form a open core composite supply. The apparatus also has one or more angled surfaces positioned to create one or more obtuse angles in the open core composite supply, and one or more folders to further fold the one or more obtuse angles in the open core composite supply to form a folded core composite supply.

FIELD OF THE INVENTION

[0001] The present invention relates generally to systems and methodsfor manufacturing absorbent garment cores. More specifically, thepresent invention relates to a system and method for forming tow-basedabsorbent structures having a single casing sheet.

BACKGROUND OF THE INVENTION

[0002] Disposable absorbent garments such as infant diapers or trainingpants, adult incontinence products and other such products typicallywere constructed with a moisture-impervious outer backsheet, amoisture-pervious body-contacting inner topsheet, and amoisture-absorbent core sandwiched between the liner and backsheet.

[0003] Much effort has been expended to find cost-effective materialsfor absorbent cores that display good liquid absorbency and retention.Particles of superabsorbent materials (SAP) in the form of granules,beads, fibers, bits of film, globules, etc., have been favored for suchpurposes. Such SAP materials generally are polymeric gelling materialsthat are capable of absorbing and retaining even under moderate pressurelarge quantities of liquid, such as water and body wastes, relative totheir weight. The SAP particles typically have been distributed within afibrous web of fluffed pulp material, which may comprise natural orsynthetic fibers. Such absorbent structures are commonly referred to asfluff pulp/SAP cores.

[0004] Superabsorbent material generally is a water-insoluble butwater-swellable polymeric substance capable of absorbing water in anamount that is greater than the weight of the substance in its dry form.In one type of superabsorbent material, the particles may be describedchemically as having a back bone of natural or synthetic polymers withhydrophilic groups or polymers containing hydrophilic groups beingchemically bonded to the back bone or an intimate admixture therewith.Included in this class of materials are modified polymers such as sodiumneutralized cross-linked polyacrylates and polysaccharides including,for example, cellulose and starch and regenerated cellulose that aremodified to be carboxylated, phosphonoalkylated, sulphoxylated orphosphorylated, causing the SAP to be highly hydrophilic. Such modifiedpolymers also may be cross-linked to reduce their water-solubility.

[0005] The ability of a superabsorbent material to absorb liquid isdependent upon the form, position and/or manner in which particles ofthe superabsorbent material are incorporated into the fibrous web of theabsorbent core. Whenever a particle of the superabsorbent material iswetted, it swells and forms a gel. Gel formation can block liquidtransmission into the interior of the absorbent core, a phenomenoncalled “gel blocking.” Gel blocking prevents liquid from rapidlydiffusing or wicking past the “blocking” particles of superabsorbent,causing portions of a partially hydrated core to become inaccessible tomultiple doses of urine. Further absorption of liquid by the absorbentcore must then take place via a diffusion process. This is typicallymuch slower than the rate at which liquid is applied to the core. Gelblocking often leads to leakage from the absorbent article well beforeall of the absorbent material in the core is fully saturated.

[0006] Despite the incidence of gel blocking, superabsorbent materialsare commonly incorporated into absorbent cores because they absorb andretain large quantities of liquid, even under load. However, in orderfor superabsorbent materials to function, the liquid being absorbed inthe absorbent structure must be transported to unsaturatedsuperabsorbent material. In other words, the superabsorbent materialmust be placed in a position to be contacted by liquid. Furthermore, asthe superabsorbent material absorbs the liquid it must be allowed toswell. If the superabsorbent material is prevented from swelling, suchas by being tightly constrained within the fibrous web or by pressureexerted by the swelling of adjacent superabsorbent particles, it willcease absorbing liquids.

[0007] Adequate absorbency of liquid by the absorbent core at the pointof initial liquid contact and rapid distribution of liquid away fromthis point are necessary to ensure that the absorbent core hassufficient capacity to absorb subsequently deposited liquids. Previousabsorbent cores have thus attempted to absorb quickly and distributelarge quantities of liquids throughout the absorbent core whileminimizing gel blocking during absorption of multiple doses of liquid.

[0008] Some of the more important performance attributes of an absorbentcore of a diaper (or any other absorbent garment) are functionalcapacity, rate of absorption, and core stability in use. Absorptionunder load or AUL is a good measure of functional capacity and the rateat which that absorption occurs. AUL is a function of both SAP basisweight (mass per unit area) and the composition of SAP used in thecomposite. Conventional baby diaper cores that contain only a fibrousweb of fluff pulp and a high gel strength SAP typically maintainadequate SAP efficiency if the core contains less than about 50% SAP.Fluff/SAP diaper cores containing more than 50% SAP generally result inlower SAP efficiency because of gel blocking. Although fluff/SAP coresat greater than 50% SAP can provide adequate absorbency, the overallbasis weight of the core typically must be increased to compensate forthe lower efficiency of the SAP. Increasing the basis weight decreasesthe performance/cost ratio of the absorbent core, making themuneconomical. Also, increased basis weights tend to affect the fit andcomfort of the garment, as well as impacting the packaging and shippingcosts.

[0009] Attempts to increase the relative weight of SAP by reducing thebasis weight of the conventional fluff pulp have resulted in failurebecause low density fluff pulp mats have been unable to withstand thetensile loads placed on them during the manufacturing process. Suchcores also exhibit poor wet strength, making them unstable during use,and fail to adequately secure the SAP in place. The introduction ofrelatively high integrity fibrous structure cores, however, has allowedthe basis weight of the fibrous web to be decreased without compromisingthe manufacturability and wet strength of the absorbent core. Theseabsorbent core structures have improved SAP efficiency and a loweroverall basis weight. Such absorbent cores are disclosed, for example,in U.S. Statutory Invention Registration No. H1,565 to Brodof et al.,which is incorporated by reference herein in its entirety and in amanner consistent with the present invention. These high integrityfibrous structure cores, referred to herein as “tow/SAP” cores or“tow-based” cores, typically use a continuous tow of crimped filaments.The tow may be provided to the absorbent core manufacturer in a compactform and “opened” (i.e., “bloomed” or fluffed up) prior to beingassembled into an absorbent core.

[0010] In some cases, the fibrous web of the tow/SAP core may be treatedwith a tackifying agent to adhere the SAP particles to the fibrous web.In other cases, the SAP particles may be introduced into the fibrous webwithout any adhesive, binder or tackifying agent, such as is disclosedin U.S. Pat. No. 6,068,620 issued to Chmielewski et al., which isincorporated by reference herein in its entirety and in a mannerconsistent with the present invention. Such a construction has beenreferred to as a dry-formed composite (DFC) core. A DFC core may besurrounded by a tissue layer or multiple tissue layers to form a DFClaminate structure that contains the fibrous web and SAP. One potentialdrawback with DFC cores, however, is that known methods and apparatusfor producing such cores typically require two separate tissue sheets tobe used during manufacturing to encase the tow and SAP. The use of twotissue sheets may, for example, increase the cost or complexity of themanufacturing operation.

[0011] A problem with SAP-containing fibrous cores has been to providethe SAP into the fibrous web in a controlled manner. Typical knownprocesses for creating a conventional fluff pulp/SAP core use a largeforming chamber to blend the SAP with the fluffed pulp, then convey thisblend onto a drum or screen by using a vacuum. The drum or screen hasforming pockets that form the fluff pulp/SAP material into the desiredshape and the formed cores then are deposited for integration intoabsorbent products. Such methods have been found to be inefficientduring startup and transitions in the manufacturing line speed becausethey require a relatively large amount of time to provide a stabilizedmixture of SAP and fluff pulp, leading to the creation of a large numberof scrap products until stabilization.

[0012] Other conventional processes for forming fluff pulp/SAP coresimmerse the fluffed pulp in a fluid mixture containing SAP particles,then dry the fluff pulp/SAP mixture before integration into theabsorbent article. Such wet forming processes typically require moremanufacturing steps and are more expensive than dry forming methods.

[0013] Other feeding systems use fixed-size moving mechanical gates thatprovide a uniform amount of SAP to the absorbent core, such as isdisclosed in U.S. Pat. No. 6,139,912 to Onuschak et al., which isincorporated herein by reference in its entirety and in a mannerconsistent with the present invention. Although such devices may besuitable for providing an even flow of SAP or other powdered andparticulate additives to absorbent cores, they rely on relativelycomplex feeding machinery, including a rotary valve that uses apneumatic SAP conveyor to return undistributed SAP back to a supplycontainer. Pneumatic conveyors typically require a relatively long timeto become pressurized and to convey the SAP, causing inefficienciesduring transitional phases, such as when the machine operating speedvaries, such as during start-up and shut-down, or when it is desired tochange the amount of SAP being fed to the core. The additional parts ofsuch feeders may also be expensive and subject to wear and other serviceproblems. Similar devices, having similar deficiencies, are disclosed inU.S. Pat. No. 4,800,102 to Takada, which is incorporated herein byreference in its entirety and in a manner consistent with the presentinvention.

[0014] Still other feeding systems use pneumatic particle projectorsthat use pressurized gas to convey the SAP to the surface of theabsorbent core. Such devices are disclosed, for example, in U.S. Pat.Nos. 5,614,147 to Pelley and 5,558,713 to Siegfried et al., which areincorporated herein by reference in their entirety and in a mannerconsistent with the present invention. Such systems rely on relativelycomplex air conveyors, that may be susceptible to blockage and may notefficiently accommodate as wide a variety of particulate, powder andfibrous materials as other systems due to their relatively small passagesizes. Indeed, it has been found that the compressed air used in suchpneumatic conveyors is often contaminated with oil that may causeblockage, SAP degradation, and other problems. Such systems may alsorequire a relatively long time to stabilize, leading to inefficienciesduring transitional phases.

[0015] Other known SAP feeding systems are disadvantageous for a numberof reasons. First, the mixture of fiber and SAP still is subject tolocal concentrations and shortages of SAP. Second, these feeding systemstypically can not be controlled accurately enough to provideconcentrations and shortages of SAP when they are desired. Third, suchfeeding systems can not be controlled to accurately provide reduced SAPamounts that are necessary during transitional phases, leading toimproperly loaded cores during those phases of operation.

[0016] These are just a few of the disadvantages of the prior art whichthe preferred embodiments seek to address. The foregoing description ofcertain material, methods and systems with their attendant disadvantagesin no way is meant to infer that the present invention excludes suchmaterials, methods, and systems. Indeed, certain embodiments of theinvention may solve some of the aforementioned disadvantages, yetutilize the same or similar materials, methods and/or systems.

SUMMARY OF THE INVENTION

[0017] It would be desirable to provide an apparatus and method forforming tow-based absorbent structures, such as absorbent cores, thathave only a single tissue sheet that encases the entire absorbent corestructure. It would further be desirable for such an apparatus andmethod to be efficient, easy to operate, and capable of operating athigh line speeds. In accordance with these and other features of variousembodiments of the invention, there is provided an apparatus and methodfor forming tow-based absorbent cores having a single casing sheet.

[0018] In accordance with one embodiment of the invention, there isprovided an apparatus having a tow supply mechanism for providing towmaterial, a particulate matter supply mechanism for providingparticulate matter, a casing sheet supply mechanism for providing casingsheet material, and a vacuum draw roll positioned to combined the tow,particulate matter and casing sheet into and open core composite supply.The vacuum draw roll has a foraminous center surface having a widthdefined by a first edge and a second edge, and the vacuum draw roll isrotatable about a first axis. In addition, one or more angled surfacesare provided and positioned to create one or more obtuse angles in theopen core composite supply, and one or more folders are provided tofurther fold the one or more obtuse angles in the open core compositesupply to form a folded core composite supply.

[0019] In accordance with another embodiment of the invention, there isprovided an apparatus for forming absorbent structures having a singlecasing sheet, that has a casing sheet supply mechanism for providingcasing sheet material, a tow supply mechanism for providing towmaterial, and a particulate matter supply mechanism for providingparticulate matter. In this embodiment, the particulate matter supplymechanism is positioned to deposit the particulate matter onto thecasing sheet material. In this embodiment the apparatus has a vacuumdraw roll having a foraminous center surface, the foraminous centersurface having a width defined by a first edge and a second edge andbeing rotatable about a first axis. The vacuum draw roll is positionedafter the particulate matter supply mechanism to deposit the towmaterial onto the casing sheet material to form a open core compositesupply. In addition, this embodiment has one or more folders to fold theopen core composite supply into a folded core composite supply.

[0020] In various embodiments of the invention, the tow material iscellulose acetate, the particulate matter is superabsorbent particles,and the casing sheet materials is tissue. In other embodiments, theparticulate matter supply mechanism is a vibratory feeder and the towsupply mechanism is a tow forming jet.

[0021] In yet another embodiment, the casing sheet material has a centerregion and first and second side regions located on opposite sides ofthe center region. The first side region extends from a first side ofthe center region to a first edge of the casing sheet material, and thesecond side region extends from a second side of the center region to asecond edge of the casing sheet material. In this embodiment, the casingsheet material is wider than the tow material, the tow material ispositioned adjacent to the center region of the casing sheet material inthe open core composite supply, and the one or more angled surfaces arepositioned to create a first obtuse angle at or near to the first sideof the center region, and a second obtuse angle at or near the secondside of the center region. Adhesive applicators may be used in these orother embodiments of the invention. In one embodiment, a first adhesiveapplicator is positioned before the vacuum draw roll to apply adhesiveto the center region of the casing sheet material. In anotherembodiment, a second adhesive applicator is operatively associated withthe one or more folders and positioned to apply adhesive to at least oneof the first and second side regions of the casing sheet material.

[0022] In still other embodiments, the angled surfaces may beoperatively associated with the vacuum draw roll, and may comprise firstand second tapering surfaces that extend from respective edges of theforaminous center surface and taper inward from the center surfacetowards the axis about which the vacuum draw roll rotates.

[0023] In another embodiment, the invention may have a break drumpositioned between the vacuum draw roll and the one or more folders. Thebreak drum is rotatable about a second axis and has a center surfacethat has a width defined by a third edge and a fourth edge. The one ormore angled surfaces may, in one embodiment, be operatively associatedwith the break drum, and may be first and second tapering surfaces, thatextending from respective edges of the center surface of the break drumand taper inward from the center surface towards the axis about whichthe break drum rotates.

[0024] In another embodiment, the invention includes an open corecomposite supply conveyor that is positioned to convey the open corecomposite supply from the vacuum draw roll to the one or more folders.The open core composite supply conveyor may have an arcuate regionsubstantially adjacent to a sector of the vacuum draw roll.

[0025] In still another embodiment, the vacuum draw roll of theinvention may have a rotatable outer drum upon which the foraminouscenter surface is disposed, and an inner structure disposed at leastpartially within the rotatable outer drum. In such an embodiment, theone or more angled surfaces may be first and second tapering surfaces,located on the outer drum, that extend from respective edges of theforaminous center surface and taper inward towards the first axis. Theinner structure has a vacuum chamber having one or more vacuum passagesforming a vacuum zone subadjacent at least a portion of the foraminouscenter surface. The vacuum zone may have a leading edge and a trailingedge, as located relative to the direction of rotation of the rotatableouter drum, and a positive air blow-off port located at the trailingedge of the vacuum zone.

[0026] In yet another embodiment, the foraminous center surface of thevacuum draw roll may have a central vacuum region and first and secondlateral vacuum regions, that are located between the central vacuumregion and the edges of the foraminous center surface. In thisembodiment, the central vacuum region may be recessed. In thisembodiment, the tow material may have an average width approximatelyequal to or less than a width of the central vacuum region, and thecentral vacuum region may be positioned to receive substantially theentire width of the tow material. The first and second lateral vacuumregions also may be positioned to apply a vacuum to the casing sheetmaterial.

[0027] In still another embodiment, the present invention provides amethod for preparing absorbent structures that have a single casingsheet. In one embodiment, the method involves providing tow material,providing particulate matter, providing casing sheet material, andforming an open core composite supply by combining the tow material, theparticulate matter and the casing sheet material on a vacuum draw rollcomprising a foraminous center surface, the foraminous center surfacehaving a width defined by a first edge and a second edge and beingrotatable about a first axis. This method also includes creating one ormore obtuse angles in the open core composite supply using one or moreangled surfaces and, forming a folded core composite supply by foldingflat the one or more obtuse angles in the open core composite supply. Inone embodiment of the method, the open core composite supply may beformed at the same time that the one or more obtuse angles are formed init. In various other embodiments the method may further employ thevarious embodiments of the apparatus described immediately above.

[0028] These and other features of the invention will be readilyapparent from the Detailed Description that follows, along withreference to the drawings appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029]FIG. 1 is a plan view of a diaper-type absorbent garment, shownwith the effects of elastics removed for clarity;

[0030]FIG. 2 is a cross-sectional view of the garment of FIG. 1, asviewed from reference line 1-1;

[0031]FIG. 3 is a partially cut away side view of a system for dryforming absorbent cores and other structures and machinery according toa preferred embodiment of the present invention, shown in operation andin relation to a portion of an absorbent garment manufacturing line;

[0032]FIG. 4 is a partially cut away view of a feed tray according to apreferred embodiment of the present invention, shown at one end of itsrange of movement and showing the other end of its range of movement indashed lines;

[0033]FIG. 5A is a cut away view of a portion of a feed tray accordingto a preferred embodiment of the present invention;

[0034]FIG. 5B is a cut away view of a portion of another feed trayaccording to a preferred embodiment of the present invention;

[0035]FIG. 6 is a partially cut away side view of a feed tray, motor andside plates according to a preferred embodiment of the presentinvention;

[0036]FIG. 7 is an isometric view of the outlet portion of a feed trayaccording to a preferred embodiment of the present invention;

[0037]FIG. 8 is an isometric view of a combining drum according to apreferred embodiment of the present invention;

[0038]FIG. 9 is a sectional view of the vacuum surface of a combiningdrum according to a preferred embodiment of the present invention, shownoperating with the core composite adjacent the vacuum surface;

[0039]FIG. 10 is a partially exploded isometric view of anothercombining drum according to a preferred embodiment of the presentinvention;

[0040]FIG. 11 is an isometric view of yet another combining drumaccording to a preferred embodiment of the present invention;

[0041]FIG. 12 is a cross sectional view of a combining drum assemblyaccording to a preferred embodiment of the present invention as viewedfrom a direction orthogonal to the rotating axis of the combining drum,and as seen from reference line 3-3 of FIG. 13;

[0042]FIG. 13 is a cross sectional view of the combining drum assemblyof FIG. 12, as seen from reference line 2-2;

[0043]FIG. 14 is a partially cut away view of the combining drumassembly of FIG. 12, shown with the outer drum partially removed;

[0044]FIG. 15 is an isometric view of the outlet portion of a feed trayaccording to another embodiment of the present invention;

[0045]FIG. 16A is a cross-sectional view of an embodiment of anabsorbent garment having a single casing sheet;

[0046]FIG. 16B is a cross-sectional view of another embodiment of anabsorbent garment having a single casing sheet;

[0047]FIG. 17 is a side view of an embodiment of a system for formingtow-based absorbent structures with a single casing sheet;

[0048]FIG. 18A is a cross-sectional view of an embodiment of anabsorbent core assembly during processing in the apparatus of FIG. 17 asviewed along reference line 4-4 of FIG. 17, shown with the machineryremoved for clarity;

[0049]FIG. 18B is a cross-sectional view of an embodiment of anabsorbent core assembly during processing in the apparatus of FIG. 17 asviewed along reference line 5-5 of FIG. 17, shown with the machineryremoved for clarity;

[0050]FIG. 18C is a cross-sectional view of an embodiment of anabsorbent core assembly during processing in the apparatus of FIG. 17 asviewed along reference line 6-6 of FIG. 17, shown with the machineryremoved for clarity;

[0051]FIG. 19 is a drawing of an embodiment of a tapered break roll ofthe embodiment of the apparatus of FIG. 17;

[0052]FIG. 20 is a drawing of an embodiment of angled surfaces and anuntapered break drum that may be used with the embodiment of FIG. 17;

[0053]FIG. 21 is a side view of another embodiment of a system forforming tow-based absorbent structures with a single casing sheet;

[0054]FIG. 22 is a side view of still another embodiment of a system forforming tow-based absorbent structures with a single casing sheet;

[0055]FIG. 23 is a top view of an embodiment of a stepped lay on rollthat may be used with a tapered vacuum draw roll in a system for formingtow-based absorbent structures with a single casing sheet;

[0056]FIG. 24 is an isometric view of an embodiment of a tapered vacuumdraw roll that may be used in a system for forming tow-based absorbentstructures with a single casing sheet;

[0057]FIG. 25 is a cut away side view of the embodiment of a taperedcombining drum of FIG. 24;

[0058]FIG. 26 is a partially cut away front view of the embodiment of atapered combining drum of FIG. 24;

[0059]FIG. 27 is a partially cut away front view detail drawing of theembodiment of a tapered combining drum of FIG. 24;

[0060]FIG. 28 is a side view of another embodiment of a system forforming tow-based absorbent structures with a single casing sheet;

[0061]FIG. 29 is a side view of yet another embodiment of a system forforming tow-based absorbent structures with a single casing sheet; and,FIG. 30 is a side view of yet another embodiment of a system for formingtow-based absorbent structures with a single casing sheet.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0062] As used herein, the term “absorbent garment” or “garment” refersto garments that absorb and contain exudates, and more specifically,refers to garments that are placed against or in proximity to the bodyof the wearer to absorb and contain the various exudates discharged fromthe body. A non-exhaustive list of examples of absorbent garmentsincludes diapers, diaper covers, disposable diapers, training pants,feminine hygiene products and adult incontinence products. The termgarment includes all variations of absorbent garments, includingdisposable absorbent garments that are intended to be discarded orpartially discarded after a single use (i.e., they are not intended tobe laundered or otherwise restored or reused) and unitary disposableabsorbent garments that have essentially a single structure (i.e., donot require separate manipulative parts such as a diaper cover andinsert). As used herein, the term “diaper” refers to an absorbentgarment generally worn by infants and incontinent persons about thelower torso.

[0063] The claims are intended to cover all of the foregoing classes ofabsorbent garments, without limitation, whether disposable, unitary orotherwise. The invention will also be understood to encompass, withoutlimitation, all other types of absorbent structure that may comprise anabsorbent core, whether described herein or not. Preferably, theabsorbent core or the garment is thin in order to improve the comfortand appearance of a garment. The importance of thin, comfortablegarments is disclosed, for example, in U.S. Pat. No. 5,098,423 toPieniak et al., which is incorporated herein by reference in itsentirety and in a manner consistent with the present invention.

[0064] Absorbent garments and diapers may have a number of differentconstructions. In each of these constructions it is generally the casethat an absorbent core is disposed between a liquid pervious,body-facing topsheet, and a liquid impervious, exterior facingbacksheet. In some cases, one or both of the topsheet and backsheet maybe shaped to form a pant-like garment. In other cases, the topsheet,backsheet and absorbent core may be formed as a discrete assembly thatis placed on a main chassis layer and the chassis layer is shaped toform a pant-like garment. The garment may be provided to the consumer inthe fully assembled pant-like shape, or may be partially pant-like andrequire the consumer to take the final steps necessary to form the finalpant-like shape. In the case of training pant-type garments and mostadult incontinent products, the garment is provided fully formed withfactory-made side seams and the garment is donned by pulling it up thewearer's legs. In the case of diapers, a caregiver usually wraps thediaper around the wearer's waist and joins the side seams manually byattaching one or more adhesive or mechanical tabs, thereby forming apant-like structure. For clarity, the present invention is describedherein only with reference to a diaper-type garment in which thetopsheet, backsheet and absorbent core are assembled into a structurethat forms a pant-like garment when secured on a wearer using fasteningdevices, although the invention may be used with other constructions.

[0065] Throughout this description, the expressions “upper layer,”“lower layer,” “above” and “below,” which refer to the variouscomponents included in the absorbent garments of the invention(including the layers surrounding the absorbent core units), as well asthe depiction in the drawings of certain layers or materials that are“above” or “below” one another, are used merely to describe the spatialrelationship between the respective components. The upper layer orcomponent “above” the other component need not always remain verticallyabove the core or component, and the lower layer or component “below”the other component need not always remain vertically below the core orcomponent. Indeed, embodiments of the invention include variousconfigurations whereby the core may be folded in such a manner that theupper layer ultimately becomes the vertically highest and verticallylowest layer at the same time. Other configurations are contemplatedwithin the context of the present invention.

[0066] The term “component” can refer, but is not limited, to designatedselected regions, such as edges, corners, sides or the like; structuralmembers, such as elastic strips, absorbent pads, stretchable layers orpanels, layers of material, or the like; or a graphic, embossed pattern,or the like.

[0067] Throughout this description, the term “disposed” and theexpressions “disposed on,” “disposing on,” “disposed in,” “disposedbetween” and variations thereof (e.g., a description of the articlebeing “disposed” is interposed between the words “disposed” and “on”)are intended to mean that one element can be integral with anotherelement, or that one element can be a separate structure bonded to orplaced with or placed near another element. Thus, a component that is“disposed on” an element of the absorbent garment can be formed orapplied directly or indirectly to a surface of the element, formed orapplied between layers of a multiple layer element, formed or applied toa substrate that is placed with or near the element, formed or appliedwithin a layer of the element or another substrate, or other variationsor combinations thereof.

[0068] Throughout this description, the terms “top sheet” and “backsheet” denote the relationship of these materials or layers with respectto the absorbent core. It is understood that additional layers may bepresent between the absorbent core and the top sheet and back sheet, andthat additional layers and other materials may be present on the sideopposite the absorbent core of either the top sheet or the back sheet.

[0069] Throughout this description, the expression “fibrous material”denotes any fibrous material that may be used in an absorbent garment,including without limitation, various hardwood and softwood fluff pulps,tissues, cottons, and any other fibrous materials described herein.“Fibrous material” used in the context of the present invention is notintended to limit the invention to any particular type of fibrousmaterial.

[0070] Throughout this description, the expression “tow fibers” relatesin general to any continuous fiber. Tow fibers typically are used in themanufacture of staple fibers, and preferably are comprised of syntheticthermoplastic polymers. Usually, numerous filaments are produced by meltextrusion of the molten polymer through a multi-orifice spinneret duringmanufacture of staple fibers from synthetic thermoplastic polymers inorder that reasonably high productivity may be achieved. The groups offilaments from a plurality of spinnerets typically are combined into atow which is then subjected to a drawing operation to impart the desiredphysical properties to the filaments comprising the tow.

[0071] A preferred embodiment of the present invention comprises adisposable absorbent garment 10 of the diaper type, such as shown, forexample, in FIG. 1. It should be understood, however, that the presentinvention is applicable to other types of absorbent garments. Withreference to FIG. 1, the diaper 10 according to a first preferredembodiment is shown in a relaxed condition with the effects of theelastics removed for purposes of clarity in the description. The diaper10 has a generally hourglass shape and can generally be defined in termsof a front waist region 22, a back waist region 24, and a crotch region26. Those skilled in the art will recognize that “front” and “back” arerelative terms, and these regions may be transposed without departingfrom the scope of the present invention. Alternatively, the diaper canbe configured in a generally rectangular shape or in a “T” shape. A pairof leg openings 28 a, 28 b extend along at least a portion of the crotchregion 26. The diaper preferably comprises a topsheet 2, a backsheet 4,which may be substantially coterminous with the topsheet 2, and anabsorbent core 6 disposed between at least a portion of the topsheet 2and backsheet 4. One or more pairs of leg elastics 8 (three pairs areshown in FIG. 1) may be disposed to extend adjacent to leg openings 28a, 28 b, respectively. Of course, in other embodiments, the leg elastics8 may be omitted altogether.

[0072] The diaper may further include a front waist elastic system 30 a,a back waist elastic system 30 b, a fastening system 32 (e.g., tape orother suitable mechanical fastener) and a waste containment system inthe form of waste containment flaps 12 (also known as standing leggathers). Waste containment flaps 12 (FIG. 2) preferably extend from thefront waist region 22 to the back waist region 24 along opposite sidesof a longitudinal center line or axial center line 60 of the diaper 10,or alternatively only along a portion thereof. The front waist region 22and rear waist region 24 may include ear portions 38,40 extendingoutwardly from the leg openings 28 a, 28 b.

[0073] A variety of backsheet and topsheet constructions and materialsare available and known in the art, and the invention is not intended tobe limited to any specific materials or constructions of thesecomponents. The backsheet 4 is of any suitable pliable liquid-imperviousmaterial known in the art. Typical backsheet materials include films ofpolyethylene, polypropylene, polyester, nylon, and polyvinyl chlorideand blends of these materials. For example, the backsheet can be apigmented polyethylene film having a thickness in the range of 0.02-0.04mm. The moisture-pervious topsheet 2 can be any suitable relativelyliquid-pervious material known in the art that permits passage of liquidtherethrough. Non-woven topsheet materials are exemplary because suchmaterials readily allow the passage of liquids to the underlyingabsorbent core 6. Examples of suitable topsheet materials includenon-woven spunbond or carded webs of polypropylene, polyethylene, nylon,polyester and blends of these materials.

[0074] The backsheet 4 and the topsheet 2 preferably are “associated”with one another. The term “associated” encompasses configurationswhereby the topsheet 2 is directly joined to the backsheet 4 by affixingthe topsheet 2 directly to the backsheet 4, and configurations wherebythe topsheet 2 is indirectly joined to the backsheet 4 by affixing thetopsheet 2 to intermediate members which in turn are affixed to thebacksheet 4. While the backsheet 4 and topsheet 2 in the preferredembodiment have substantially the same dimensions, they may also havedifferent dimensions.

[0075] In addition, the backsheet 4 may be covered with a fibrous,nonwoven fabric such as is disclosed for example in U.S. Pat. No.4,646,362, which is incorporated herein by reference in its entirety andin a manner consistent with the present invention. Materials for such afibrous outer liner include a spun-bonded nonwoven web of syntheticfibers such as polypropylene, polyethylene or polyester fibers; anonwoven web of cellulostic fibers, textile fibers such as rayon fibers,cotton and the like, or a blend of cellulostic and textile fibers; aspun-bonded nonwoven web of synthetic fibers such as polypropylene;polyethylene or polyester fibers mixed with cellulostic, pulp fibers, ortextile fibers; or melt blown thermoplastic fibers, such as macro fibersor micro fibers of polypropylene, polyethylene, polyester or otherthermoplastic materials or mixtures of such thermoplastic macro fibersor micro fibers with cellulostic, pulp or textile fibers.

[0076] The backsheet 4 may comprise multiple panels, such as threepanels wherein a central poly backsheet panel is positioned adjacent theabsorbent core while outboard non-woven breathable side backsheet panelsare attached to the side edges of the central poly backsheet panel. Thebacksheet may also be formed from microporous poly coverstock for addedbreathability. In other embodiments, the backsheet may be a laminate ofseveral sheets. The backsheet may further be treated to render ithydrophilic or hydrophobic, and may have one or more visual indicatorsassociated with it, such as labels indicating the front or back of thediaper or other characters or colorations. The present invention is notlimited to any particular backsheet 4 material or construction.

[0077] The topsheet 2 may be formed from one or more panels of materialand may comprise a laminated sheet construction. In the embodiment ofFIG. 1, the topsheet comprises three separate portions or panels. Athree-panel topsheet may comprise a central topsheet panel 2 a (FIG. 2)that preferably is formed from a liquid-pervious material that is eitherhydrophobic or hydrophilic. The central topsheet panel 2 a may be madefrom any number of materials, including synthetic fibers (e.g.,polypropylene or polyester fibers), natural fibers (e.g., wood orcellulose), apertured plastic films, reticulated foams and porous foamsto name a few. One preferred material for a central topsheet panel 2 ais a cover stock of single ply non-woven material which may be made ofcarded fibers, either adhesively or thermally bonded, perforated plasticfilm, spunbonded fibers, or water entangled fibers, which generallyweigh from 0.3-0.7 oz./yd² and have appropriate and effective machinedirection and cross-machine direction strength suitable for use as ababy diaper cover stock material, as are known in the art. The centraltopsheet panel 2 a preferably extends from substantially the front waistregion 22 to the back waist region 24 or a portion thereof.

[0078] The second and third topsheet panels 2 b, 2 c in this embodimentmay be positioned laterally outside of the central topsheet panel 2 a.The outer topsheet panels 2 b, 2 c preferably are substantiallyliquid-impervious and hydrophobic, preferably at least in the crotcharea. The outer edges of the outer topsheet panels may substantiallyfollow the corresponding outer perimeter of the backsheet 4. Thematerial for the outer topsheet portions or panels preferably ispolypropylene and can be woven, non-woven, spunbonded, carded or thelike, depending on the application.

[0079] An inner region 34 (FIG. 2) of the outer topsheet portions orpanels 2 b, 2 c preferably is attached by, e.g., an adhesive, to theouter edges 36 of the inner topsheet portion or panel 2 a. At the pointof connection with the outer edges 36 of the inner topsheet portion orpanel 2 a, the inner regions 34 of the outer topsheet portions or panels2 b, 2 c extend upwardly to form waste containment flaps 12. The wastecontainment flaps 12 may be formed of the same material as the outertopsheet portions or panels 2 b, 2 c, as in the embodiment shown. Thewaste containment flaps 12 may also be formed from separate elasticizedstrips of material that are associated with the topsheet, backsheet orboth, or otherwise integrated into the garment.

[0080] The waste containment flaps 12 may be treated with a suitablesurfactant to modify their hydrophobicity/hydrophilicity or imbue themwith skin wellness products as desired. The central topsheet portion orpanel 2 a may extend past the connection point with the wastecontainment flaps 12 and even extend to the periphery of the backsheet.Still further, the central topsheet portion or panel 2 a could extendfully between the outer topsheet portions or panels 2 b, 2 c and evenbeyond so that the outer edges 36 of the central topsheet portion orpanel 2 a are coextensive with and sandwiched between the outer topsheetportions or panels 2 b, 2 c and the backsheet 4.

[0081] The waste containment flaps 12 each preferably includes a portionthat folds over onto itself to form an enclosure. One or more elasticmembers 14 (FIG. 2) may be secured in the enclosure in a stretchedcondition. As has been known at least as long the disclosure ofTetsujiro, Japanese Patent document 40-11543, when the flap elastic 14attempts to assume the relaxed, unstretched condition, the wastecontainment flaps 12 rise above the surface of the central topsheetportion or panel 2 a. Various other configurations of topsheets 2 andwaste containment systems, such as flaps 12, are known in the art, andthe present invention is not intended to be limited to any particulardesign for these components.

[0082] The waist elastics 30 a, 30 b (FIG. 1) may be similar structuresor different to impart similar or different elastic characteristics tothe front and back waist portions 22, 24 of the diaper. In general, thewaist elastics may comprise elastically extensible foam stripspositioned at the front and back waist sections 22, 24. The foam stripsare preferably about 0.50 inches to about 1.50 inches wide and about 3inches to about 6 inches long. The foam strips are preferably positionedbetween the topsheet portions or panels and the backsheet 4.Alternatively, a plurality of elastic strands may be employed as waistelastics rather than foam strips. The foam strips are preferablypolyurethane, but could be any other suitable material that preferablydecreases waist band roll over, reduces leakage over the waist ends ofthe absorbent garment, and generally improves comfort and fit. The frontand back waist foam strips 30 a, 30 b are stretched 50-150%, preferably100% before being adhesively secured between the backsheet 4 andtopsheet 2. Waist elastics are known in the art, and the presentinvention is not limited to the use of a particular waist elasticsystem, or to the inclusion of waist elastics at all.

[0083] Each leg opening 28 a, 28 b may be provided with a leg elasticcontainment system 8, sometimes referred to as conventional leg gathers.In a preferred embodiment, three strands of elastic threads arepositioned to extend adjacent the leg openings 28 a, 28 b between theouter topsheet portions or panels 2 b, 2 c and the backsheet 4 theselection of appropriate elastics and the construction of leg elasticcontainment systems is known in the art. For example, the leg elastics 8may be ultrasonically bonded, heat/pressure sealed using a variety ofbonding patterns, or glued to the diaper 10.

[0084] Various commercially available materials may be used for the legelastics 8 and elastic members 14, such as natural rubber, butyl rubberor other synthetic rubber, urethane, elastomeric materials such asspandex, which is marketed under various names, including LYCRA(DuPont), GLOSPAN (Globe) and SYSTEM 7000 (Fulflex), and so on. Thepresent invention is not limited to any particular elastic.

[0085] The fastening system of the diaper 10 may be attached to the backwaist region 24, and preferably comprises tape tabs or mechanicalfasteners 32. However, any fastening known in the art will beacceptable. Moreover, the fastening system may include a reinforcementpatch below the front waist portion so that the diaper may be checkedfor soiling without compromising the ability to reuse the fastener.Alternatively, other diaper fastening systems are also possible,including safety pins, buttons, and snaps. Fastening systems are knownin the art, and the present invention is not limited to using anyparticular fastening, and may be constructed without any fasteningsystem at all, such as in training pant-type garments.

[0086] As stated previously, the invention has been described inconnection with a diaper. The invention, however, is not intended to belimited to application only in diapers. Specifically, the presentinvention may be readily adapted for use in other absorbent garmentsbesides diapers, including, but not limited to, training pants, femininehygiene products and adult incontinence products.

[0087] The underlying structure beneath the topsheet 2 may include,depending on the diaper construction, various combinations of elements,but in each embodiment, it is contemplated that the absorbent garmentwill preferably include an absorbent core 6. For example, an additionallayer 20 may be disposed between the topsheet 2 and absorbent core 6, asshown in FIG. 2, and/or other additional layers may be disposed betweenthese layers, or between absorbent core 6 and backsheet 4. Theadditional layer 20 or layers may comprise any useful layer known in theart or developed hereafter, such as a fluid acquisition layer, adistribution layer, an additional fibrous layer optionally containingSAP, a wicking layer, a storage layer, or combinations and fragments ofthese layers. Such layers may be provided to assist with transferringfluids to the absorbent core 6, handling fluid surges, preventing rewet,containing absorbent material, improving core stability, or for otherpurposes. Skilled artisans are familiar with the various additionallayers that may be included in an absorbent article, and the presentinvention is not intended to be limited to any particular type ofmaterials used for those layers. Rather, the invention encompasses alltypes of wicking layers, all types of distribution layers, etc., to theextent that type of layer 20 is utilized.

[0088] The dimensions of additional layer(s) 20 may be the same as ordifferent from the dimensions of the absorbent core 6 and/or topsheet 2and backsheet 4. It is preferred that additional layer(s) 20 have awidth in the lateral direction (102) of anywhere from about 10 mm toabout 100 mm, and preferably from about 25 mm to about 80 mm.

[0089] Although the absorbent core 6 depicted in FIG. 1 has asubstantially rectangular shape as viewed in the plan view, other shapesmay be used, such as a “T” shape or an hourglass shape. The absorbentcore 6 may extend into either or both of the front and back waistregions 24, 22. The shape and construction of the absorbent core 6 maybe selected to provide the greatest absorbency in target areas wherebody fluids are most likely to strike the diaper 10, which is oftenreferred to as zoned absorbency. The absorbent core 6 may also comprisea number of layers of similar or different construction. The absorbentcore may be associated with the topsheet 2, backsheet 4, or any othersuitable part of the garment 10 by any method known in the art, in orderto fix the absorbent core 6 in place.

[0090] Generally, in a preferred embodiment, the absorbent core 6comprises particles of super absorbent polymer distributed within afibrous structure. Additional fibrous or particulate additives may bedisposed within the absorbent core 6 to add to the core's strength andSAP efficiency or to otherwise enhance the performance of the garment.The absorbent core 6 may be partially or wholly surrounded by a tissuelayer 16, 18, and other additional layers 20 may be added to providefurther benefits. The various components of the absorbent core 6 are nowdescribed in greater detail.

[0091] Certain fibrous materials preferably are used to form the fibrousstructure of the absorbent core 6 of the present invention. Thesefibrous materials maintain high SAP efficiencies when the SAP weightconcentration is in the range of about 50-95%, more preferably about65-95%, and most preferably about 80-95% (as measured in the absence oftissue, glue or other core components). For example, the fibrousstructure of the absorbent core 6 may be made with cellulose acetatefibers, polypropylene fibers, rayon fibers, Courtauld's LYOCELL fibers,polyacrylonitrile fibers, surface-modified (hydrophilic) polyesterfibers, surface-modified polyolefin/polyester bicomponent fibers,surface-modified polyester/polyester bicomponent fibers, cotton fibers,blends of the foregoing materials, and the like.

[0092] Of the foregoing, cellulose acetate or polyolefinic (e.g.,polypropylene or polyethylene) tow fibers are the most preferredmaterials for use as the fibrous structure. In addition, rayon,Courtauld's LYOCELL, polyacrylonitrile, cotton fibers and cotton lintershave similar properties to cellulose acetate and are alternativelypreferred. The remaining fibers, surface-modified polyolefin/polyesterbicomponent fibers, and surface-modified polyester/polyester bicomponentfibers are also believed to be effective as a fibrous structure or asfibrous additives. Of course, other fibers may also be used. To maintainhigh SAP concentrations, the weight concentration of fibrous materialforming the absorbent core 6 of the invention preferably is about 5-50%,more preferably about 5-35%, and most preferably about 5-20% (asmeasured in the absence of tissue, glue or other core components). Mostpreferably, the absorbent core 6 comprises from about 80-95% SAP andfrom about 5-20% fibrous structure material chosen from the foregoinggroup.

[0093] In accordance with the present invention, improved absorbentarticles are advantageously based upon continuous crimped filament tow,and accordingly, the central fibrous structure of the core 6 isadvantageously prepared therefrom. This fiber structure has highstructural integrity, and as such, is distinct from a matrix ofdiscontinuous fibers, often described as fluff or fluff pulp, that iscommonly used in the prior art. The high structural integrity enablesthe production of stronger webs than those formed from discontinuousfibers, which in turn are believed to enable the production of thinnerabsorbent pads. In addition, the use of such fibers enables theproduction of ultra low density absorbent cores, when compared toabsorbent cores prepared by dispersing SAP particles in fluff. Thereduction in density is largely attributable to the reduced weight ofthe fibrous structure. Absorbent cores 6 constructed from a blend ofsuch materials and SAP are referred to herein as “tow/SAP” cores or“tow-based” cores.

[0094] Beneficially, cellulose ester tow is used to form the fibrousstructure. Non-limiting examples of suitable cellulose esters includecellulose acetate, cellulose propionate, cellulose butyrate, cellulosecaproate, cellulose caprylate, cellulose stearate, highly acetylatedderivatives thereof such as cellulose diacetate, cellulose triacetateand cellulose tricaproate, and mixtures thereof such as celluloseacetate butyrate. A suitable cellulose ester preferably will have theability to absorb moisture, is biodegradable, and is influenced not onlyby the substituent groups but also by the degree of substitution. Therelationship between substituent groups, degree of substitution andbiodegradability is discussed in W. G. Glasser et al, BIOTECHNOLOGYPROGRESS, vol. 10, pp. 214-219 (1994), the disclosure of which isincorporated herein by reference in its entirety.

[0095] Alternatively, a polyolefinic fiber tow may be used beneficiallywith the present invention. Polyolefinic fibers offer certainadvantages, for example, they are typically available in a wider denierrange than other materials and they are thermoplastic and thus can beembossed. In addition, polyolefinic fibers have a relatively highresiliency, making more able to spring back after being placed underpressure. Such resiliency is beneficial because it creates a bufferbetween the wearer and the wetted SAP that reduces rewet values andmakes the garment more comfortable.

[0096] Typically, the denier per fiber (dpf) of the tow fiber will be inthe range of about 1 to 30, preferably about 7 to 15, and mostpreferably about 10. For the same weight product, filaments of lower dpfmay provide increased surface area and increased moisture absorption.Total denier of the tow may vary within the range of about 5,000 to80,000, depending upon the process and material used, and is preferablyabout 30,000. Lower total deniers provide a more open structure thatallows free transfer of fluid, while higher total deniers tend toobstruct the movement of fluid and rely more on capillary fluidconveyance. The total denier should not be excessively reduced, however,as this may result in inadequate core strength, reduced resiliency(leading to increased rewet), and reduced comfort. The foregoing dpfsand total deniers are beneficial for cellulose acetate tows andpolyolefinic fiber tows. Of course, other dpfs and total deniers may beselected according to the particular material used for the fiber. Thefibers may have a circular, ovate, rectilinear, or any other crosssection. In one embodiment, the fibers have a tri-lobal cross sectionwith an area of about 3.36×10⁻⁶ cm². Such a cross-sectional shape mayprovide improved bending stiffness, increased wicking, or otherbeneficial properties.

[0097] Tow typically is provided as a relatively dense matrix of fibers,and it is often desirable to “open” (also known as “fluffing” or“blooming”) the tow into a more voluminous cotton-like matrix. Variousmethods and devices for opening tow are known in the art. For example,U.S. Pat. No. 4,468,845 to Harris discloses a tow forming jet having ajet portion that injects gasses into the tow that cause the tow toseparate when the gasses escape, and a bustle portion that collects thetow into a cotton-like mass, thereby essentially completing the bloomingoperation. Another device, disclosed in U.S. Pat. No. 6,253,431,operates without a dancer (i.e. tension plate). These or any other towopening device may be used with the present invention.

[0098] Tow having crimped filaments may be used with the presentinvention, as the crimps aid with opening the tow. The separation offilaments resulting from the opening process advantageously results inincreased available filament surface area for superabsorbent materialimmobilization and increased moisture absorption. Gel blocking also maybe reduced by using crimped tow in the absorbent core 6. As thereforemay be understood, more crimp is typically better, with an excess ofabout 20 crimps per inch being usually preferred. Continuous filamentcellulose ester tow having crimped filaments with about 25 to 40 crimpsper inch is commercially available from Hoechst Celanese Corporation ofCharlotte, N.C. However, it should be understood that uncrimped towfilaments or filaments having relatively few crimps also may be usedwith the present invention, and may provide a cost advantage withoutsubstantially reducing the performance of the garment.

[0099] If desired, an absorbent core 6 of multiple layer thickness maybe provided. To this end, the tow may be, for example, lapped orcrosslapped in accordance with conventional procedures. In this way, asuperabsorbent, absorptive material of a desired weight and/or thicknessmay be provided. The specific weight or thickness will depend uponfactors including the particular end use.

[0100] Any superabsorbent polymer (SAP) now known or later discoveredmay be used in the absorbent core 6, so long as it is capable ofabsorbing liquids. In addition, the SAP may be omitted from the core 6in some circumstances, such as when a swim garment is produced. UsefulSAP materials are those that generally are water-insoluble butwater-swellable polymeric substances capable of absorbing water in anamount that is at least ten times the weight of the substance in its dryform. In one type of SAP, the particles or fibers may be describedchemically as having a back bone of natural or synthetic polymers withhydrophilic groups or polymers containing hydrophilic groups beingchemically bonded to the back bone or in intimate admixture therewith.Included in this class of materials are such modified polymers as sodiumneutralized cross-linked polyacrylates and polysaccharides including,for example, cellulose and starch and regenerated cellulose which aremodified to be carboxylated, phosphonoalkylated, sulphoxylated orphosphorylated, causing the SAP to be highly hydrophilic. Also includedare water swellable polymers of water soluble acrylic or vinyl monomerscrosslinked with a polyfunctional reactant. Such modified polymers mayalso be crosslinked to reduce their water-solubility, and suchcross-linked SAPs have been found to provide superior performance insome absorbent cores. A more detailed recitation of superabsorbentpolymers is found in U.S. Pat. No. 4,990,541 to Nielsen, the disclosureof which is incorporated herein by reference in its entirety. The SAP ispreferably selected to provide high absorbency performance for theparticular application. The measure of the SAP's absorbency performancemay be evaluated in a number of ways, as will be understood by thoseskilled in the art. For example, it may be desirable, in some cases, toprovide a SAP having a high measure of saline flow conductivity (SFC),as is described in U.S. Pat. No. 5,562,646 to Goldman et. al, which isincorporated herein by reference in its entirety and in a mannerconsistent with the present invention. However, the present invention isalso suitable for providing a low saline flow conductivity, which alsomay provide certain benefits, such as higher capacity and absorbencyunder load. Of course, the SAP may be selected to provide otherproperties or combinations of properties as well.

[0101] Commercially available SAPs include a starch modifiedsuperabsorbent polymer available under the trade name SANWET from BASFof Portsmouth, Va. SANWET is a starch grafted polyacrylate sodium salt.Other commercially available SAPs include a superabsorbent derived frompolypropenoic acid, available under the trade name DRYTECH 520SUPERABSORBENT POLYMER from The Dow Chemical Company, Midland Mich.;AQUA KEEP manufactured by Seitetsu Kagaku Co., Ltd.; ARASORBmanufactured by Arakawa Chemical (U.S.A.) Inc.; and FAVOR manufacturedby Stockhausen Inc. Still other commercially available SAPs includeSA55SX, available from Sumitomo Chemical Co. Ltd. of Osaka, Japan, and3900, 8400 and 8600 provided by BASF of Portsmouth, Va.

[0102] The SAP may be provided in any particle size, and suitableparticle sizes vary greatly depending on the ultimate propertiesdesired. Preferably, a fine particulate rather than a coarseparticulate, is used in the invention, and preferably a fine particulatethat passes through an about 200 mesh screen is used.

[0103] It has been known to prepare absorbent cores comprised ofcellulose acetate tow or other polymeric fibers and SAP, as described inU.S. Statutory Invention Registration H1565, and U.S. Pat. Nos.5,436,066, and 5,350,370, the disclosures of each of which areincorporated by reference herein in their entirety and in a mannerconsistent with the present invention. It was conventional to addtackifying agents, specific size fibers, or specific fibers incombination with fluff, in order to prepare the absorbent core andimmobilize the SAP particles. These additional materials may add todensity of the core, or otherwise adversely affect the overallperformance of the absorbent garment made therefrom. Thus, the use ofsuch additives (or any other additives, adhesives, bonding agents or thelike) should be controlled to minimize any negative effects caused bytheir inclusion.

[0104] The total basis weight of the absorbent core 6 including fibrousmaterials, SAP, tissue, additional layers, and additives, typically maybe anywhere from about 50 grams per square meter (gsm) to about 1,000gsm. The most preferred total basis weight of the absorbent core 6 isabout 250 gsm to about 700 gsm.

[0105] Additional particles or fibrous additives may be added to theabsorbent core 6 to help maintain high SAP efficiency, to reduce thecost of the garment, or to provide other benefits. Fibrous additives maybe introduced as part of the supply of unopened tow or may be added totow after it has been opened. In a preferred embodiment, particulateadditives generally may be added to the tow after it has been opened toallow practical manufacture of the tow and to prevent losses of theparticulate additives during processing.

[0106] In one embodiment, about 1-10%, and preferably about 5%, byweight of thermally bondable synthetic fibers may be added to theabsorbent core 6 to impart additional wet strength to the laminate.These additive fibers may improve the stability of the core during useof the diaper. The preferred synthetic fibers for such an embodiment arepolyolefin/polyester fibers and polyester/polyester bicomponent fibers.

[0107] In another embodiment, the fibrous structure may comprise acombination of preferred tow materials or a combination of a towmaterial and a fluff pulp material, such as a blend of cellulose esterand conventional soft or hard wood fibers. Such combinations may beuseful to maintain the improved SAP efficiency available from thecrimped filament tow-based fibrous structure while providing additionalbenefits. For example, it has been discovered that an absorbent core 6having a 150 g/m² composite comprised of 80% SAP, 10% cellulose acetate,and 10% conventional fluff pulp has a SAP efficiency of about 85%,whereas an absorbent core 6 comprised of 80% SAP and 20% fluff pulp SAPhas an efficiency of about 70%.

[0108] The particulate additives that may be added to the absorbent core6 preferably are insoluble, hydrophilic polymers with particle diametersof 100 μm or less. These particulate additives may be chosen to impartoptimal separation of the SAP particles. Examples of preferredparticulate additive materials include, but are not limited to, potato,corn, wheat, and rice starches. Partially cooked or chemically modified(i.e., modifying hydrophobicity, hydrophilicity, softness, and hardness)starches can also be effective. Most preferably, the particulateadditives comprise partially cooked corn or wheat starch because in thisstate, the corn or wheat are rendered larger than uncooked starch and inthe cooked state remain harder than even swollen SAP. In any event,regardless of the particulate additive chosen, one of the many importantcriteria is to use particulate additives that are hard hydrophilicmaterials relative to swollen SAP or which are organic or inorganicpolymeric materials about 100 microns in diameter. Fibrous andparticulate additives can be used together in these absorbent laminates.Examples of SAP/particulate and SAP/fiber/particulate additives includethose described in, for example, U.S. Pat. No. 6,068,620.

[0109] Other particulate or powdered additives also may be depositedwithin the absorbent core 6 to provide odor control, skin wellness, andimproved appearance. For example, zeolites, sodium bicarbonate andperfumes may be added to reduce or mask odors, and titanium dioxide orother color-imbuing compounds may be added to provide the absorbent core6 with a more pleasant color.

[0110] The absorbent core 6 preferably comprises a tissue wrapping thatat least partially encloses the preferred blended tow and SAP, such asdisclosed in U.S. Pat. No. 6,068,620. The tissue wrapping is useful, forexample, for containing the SAP within the absorbent core 6 andproviding strength to the core during manufacturing and use. In apreferred embodiment, the tissue wrapping comprises first and secondtissue layers 16, 18 that encase the absorbent core 6, and mayoptionally also encase one or more additional layers 20. Preferably, thefirst tissue layer 16 is located generally between the topsheet 2 andthe absorbent core 6, and is hydrophilic and fluid pervious. It is alsopreferred that the second tissue layer 18 be located between thebacksheet 4 and the absorbent core 6 and be hydrophobic and fluidimpervious. The tissue wrapping may also comprise a single tissue layerthat has been folded to encase the absorbent core, and that may be zonetreated to render the portion that forms the lower tissue layer 18hydrophobic and fluid impervious. Embodiments having a single tissuelayer are described in more detail below, but generally may have all ofthe features described herein with reference to embodiments havingmultiple tissue layers. The tissue layers 16, 18 or the whole core 6 maybe crimped, folded, sealed or bonded to help contain the SAP particles.

[0111] In one embodiment, the tissue, fibrous structure and SAP of theabsorbent core may be adhesively or thermally bonded to improve theabsorbent core's wet strength and core stability. This may, in somecases, result in slower than adequate rates of absorption and poor SAPefficiency. In another embodiment the SAP and fibrous structure may behydrogen bonded to additional the tissue layers 16, 18. When a tow-basedfibrous structure having a high concentration of SAP is hydrogen bondedto first and second tissue layers 16, 18 to form an absorbent core 6,the SAP efficiency is not impaired, wet strength increases, and thefirst and second tissue layers 16, 18 add stability to the core 6 duringmanufacture. It has been found that when the fibrous structure of theabsorbent core 6 is hydrogen bonded using water to the tissue layers 16,18, unexpectedly good “core utilization” is realized. “Core utilization”is the percentage of the total capacity of a core that can be absorbedin a demand absorbency test. This unexpected performance improvement isbelieved to be the result of the beneficial liquid distribution providedby the intimate bond between the fibers of the fibrous structure and thetissue layers 16, 18.

[0112] In another preferred embodiment, the first and second tissuelayers 16, 18 are coated with adhesive prior to being placed on eitherside of the absorbent core 6, thereby providing strength to the core andadhesively holding a portion of the SAP in place during use. The tissuelayers 16, 18 may be provided having a width greater than the fibrousstructure of the absorbent core 6, and the portions of the tissue layers16, 18 extending past either side of the fibrous structure of the core 6may be bonded to one another to provide further SAP retentioncapability. In still another embodiment, if the fibrous structurecontains about 1-5% by weight thermally bondable synthetic fibers,bonding to the tissue layers 16, 18 may be achieved using thermal bonds.

[0113] The absorbent core 6 of the present invention may flat or foldedwhen it is fixed in place between the topsheet 2 and backsheet 4. Foldedcores may provide additional performance benefits, such as improvedfluid redistribution, greater SAP efficiency, and so on. The absorbentcore 6 can be folded in any suitable manner, including any and all ofthose disclosed in U.S. Pat. No. 6,068,620. Those skilled in the artwill appreciate that the absorbent core 6 can be folded such that theadjacent sides are touching one another, or so that channels are formedin certain areas. For example, the absorbent core 6 can be folded in theform of a “C” where the curled ends may be spaced apart to form achannel there between, and the lower edges of the curled ends may bedisposed adjacent the upper edges of the bottom portion of the foldedarticle. Alternatively, another absorbent material, or another absorbentcore 6 may be disposed in the space formed by the standard “C” fold. Thesame considerations may be given to embodiments having a “G” fold or a“U” fold where the spaces formed by these folds may be filled withanother absorbent material, another absorbent core 6, left open to formfluid handling channels, or the folds may be made tight enough so thatlittle or no space is formed. Other possible arrangements include a “Z”fold, and a pleated absorbent core 6, and other folded shapes, as willbe appreciated by those skilled in the art.

[0114] The absorbent core 6 preferably is formed using a dry process.Dry processes have numerous benefits over wet processes. For example, inwet processes, the core material is typically immersed in a fluid havinga superabsorbent particles mixed or suspended therein, and the corematerial may require additional drying steps and other steps that add tothe complexity and cost of the core forming process. In addition, wetprocesses often require the absorbent core to be manufactured off of themain assembly line. Dry processes typically have lower operating coststhan wet processes because the equipment used in dry processes istypically less complex and can run at higher line speeds. Further, dryforming processes may often be adapted for use directly on the line ofconventional diaper machines. A preferred embodiment of the presentinvention is particularly concerned with using a dry forming process tomanufacture absorbent cores having high concentrations of SAP andrelatively low basis weights, while overcoming or avoiding thedeficiencies of known dry forming processes and machines, as describedelsewhere herein.

[0115] One challenge with making absorbent cores having highconcentrations of SAP and relatively low basis weight fibrousstructures, as described above, is to achieve the desired distributionof SAP within the core. In many cases it may be desirable to achieve auniform distribution of SAP within the core to provide the absorbentgarment with uniform absorption capability. In such a case, not onlyshould the SAP be evenly distributed along the length and width of theabsorbent core, but it also should be properly distributed throughoutthe thickness of the core to ensure that the SAP is not subject to gelblocking or other inefficiencies during use. It also is desirable toprovide a controlled amount of SAP to the core to prevent overuse of theSAP, which typically is relatively expensive. It may be furtherdesirable to precisely control the distribution of SAP to provide localregions of the core that have greater SAP concentrations than others toprovide zoned absorbency. Such concentrations may be along one or moreof the absorbent core's length, width and thickness.

[0116] Referring now to FIG. 3, a preferred embodiment of an apparatusand method for dry forming composite cores is shown. In the preferredembodiment, a tow supply 302, which may be unopened or partially opened,is provided along a first path to enter a forming jet assembly 304. Thesupply of tow may comprise any material that is desired to be used asthe fibrous structure of the garment's absorbent core 6 and is suitablefor use in the process described herein, such as those that have beendescribed elsewhere herein. Those skilled in the art will appreciatethat if fibers, fluff, or pulp other than tow fibers are used, formingjet assembly 304 would be replaced by a suitable fiber or fluff formingapparatus, as are well known in the art. A preferred material for thetow supply 302 is a supply of cellulose acetate having a basis weight ofabout 50 g/m² to about 100 g/m², and more preferably of about 76 g/m².The tension, speed and path of the tow supply 302 may be adjusted by oneor more movable pulleys 306, guides (not shown) and/or festoons (notshown), as are known in the art.

[0117] The tow supply 302 enters the forming jet assembly 304 and isopened in preparation for being incorporated into absorbent cores. Theforming jet assembly 304 comprises a tow inlet 308 at one end into whichthe tow supply 302 is fed. One or more high velocity jets 310 of air orother gas are projected into the forming jet assembly to impinge uponthe tow supply 302 to thereby separate the fibers and “bloom” or openthe tow. Preferably, two jets 310 are used and each jet 310 is locatedproximal to the tow inlet 308 and on opposite sides of the tow supply302. Each of the jets 310 preferably comprises a flow of air moving atabout 17.5 cubic feet per minute through a slit-shaped port that has alength of about 3.94 inches and a width of about 0.003 inches. Similardevices for opening tow are known in the art, and disclosed, forexample, in U.S. Pat. No. 5,331,976 to St. Pierre, which is incorporatedherein by reference in its entirety and in a manner consistent with thepresent invention. Other devices and procedures for opening the towsupply 302 may also be used with the present invention, as will beunderstood by those skilled in the art.

[0118] The opened or “bloomed” tow 312 accumulates within the formingjet assembly 304 as it is being used, and the amount of opened tow 312being consumed may be measured by a level meter 314 (also known as a“dancer”). The level meter 314 may be any suitable electromechanical,optical, or other type of device capable of measuring the amount ofopened tow 312 being consumed. In a preferred embodiment, the levelmeter 314 is a plate that is pivotally attached to a rotary positionsensor (such as a commonly known variable resistance or potentialdevice). As the level of opened tow 312 increases or decreases, theplate pivots up and down, thereby changing the output of the rotaryposition sensor. In a preferred embodiment, the level meter 314 is usedas part of a closed-loop feedback algorithm or an open-loop algorithm tometer the rate at which the tow supply 302 is fed into the forming jetassembly 304, and may be integrated into a control system 320.

[0119] The control system 320 may comprise any electrical controlapparatus that may be configured to control one or more variables basedon the measurement of one or more inputs. Although the control system320 is referred to herein in the singular, it should be understood thata number of independent control systems 320 may be used for variousparts of the machinery, and these various systems are referred tocollectively herein as a single control system 320. The control system320 may control any number of variables and have any number of inputs,and may use an open-loop or closed-loop algorithm. Exemplary controlsystems 320 include programmable logic control (PLC) devices havingeasily used human machine interfaces, as are known in the art. Ofcourse, the control system 320 may simply comprise a human operator thatmonitors the various inputs and adjusts the various system variables.

[0120] The opened tow 312 preferably is pulled out of the forming jetassembly 304 by a vacuum draw roll 322, such as the combining drum 800described elsewhere herein in conjunction with FIG. 8, or a similardrawing device. The opened tow 312 exits the forming jet assembly 304 ata tow break angle Θ_(B), which may be adjusted by altering the positionof the vacuum draw roll 322 (or similar device), or, more preferably, byadjusting the height and angle of the forming jet assembly 304 usingadjustable mounts 324. Increasing the tow break angle Θ_(B) increasesthe drag on the opened tow 312 and thereby increases the amount ofstretch that the vacuum draw roll 322 imparts on the opened tow 312.Greater stretch reduces the basis weight of the opened tow 312 that ispulled onto the vacuum draw roll 322. The tow forming jet 304 preferablyis aligned so that its outlet is tangential to the vacuum draw roll 322or slightly above a tangent to the vacuum draw roll 322. In a preferredembodiment, the outlet of the tow forming jet 304 is located at atangent to the vacuum draw roll 322 to about 1 inch above a tangent tothe vacuum draw roll 322. In a more preferred embodiment the outlet ofthe tow forming jet 304 is less than about 0.75 inches above a tangentto the vacuum draw roll 322, and in a most preferred embodiment, theoutlet of the tow forming jet 304 is located less than about 0.5 inchesabove a tangent to the vacuum draw roll 322. In another embodiment, theamount of stretch on the opened tow 312 may instead (or additionally) beregulated by operating the dancer 314 as a baffle (instead of using itas a level meter 314) to pinch down on the opened tow 312 as it ispulled onto the vacuum draw roll 322, and thereby increase the stretchof the opened tow 312. By using the dancer as a baffle, it is expectedthat adjustments of up to +/−10% may be made to the tow stretch or basisweight.

[0121] The tow forming jet's adjustable mounts 324 may be fixed in adesired position during machine operation, or may be actively operatedby a control system 320 during operation in response to measurements ofthe core basis weight or other feedback gathered during operation.Mechanical, electromechanical, pneumatic, hydraulic, or other suitableadjusting devices may be used to actuate the adjustable mounts 324, suchas stepper motors, solenoids and hydraulic or pneumatic pistons or rams,and the like. Alternatively, or in addition, the basis weight of theopened tow 312 may be adjusted by increasing or decreasing the speed ofthe vacuum draw roll 322, with faster speeds generally resulting in alower basis weight of the opened tow 312.

[0122] After the opened tow 312 exits the forming jet assembly 304, asupply of superabsorbent particles 326 is delivered to the opened tow312, and the tow/SAP composite is encased between first and secondcasing sheet supplies 316, 318. Alternatively, the tow/SAP composite maybe encased within a fold in a single casing sheet. Preferably, as shownin FIG. 3, the opened tow 312 is laid onto a first casing sheet supply316 before the SAP 326 is fed to the opened tow 312 to help contain theSAP 326 and control the SAP distribution, then the second casing sheetsupply 318 is laid on the tow/SAP composite to form an absorbent coresubassembly that may be processed into absorbent garments.

[0123] The first and second casing sheet supplies 316, 318 encase theopened tow and SAP composite. The first and second casing sheet supplies316, 318 preferably form the first and second tissue layers 16, 18 ofthe completed garment, but may also form the topsheet 2 and backsheet 4of the absorbent garment 10, or any other layers. The first and secondcasing sheet supplies 316, 318 are preferably wider than the opened tow312 that forms the absorbent core 6, and their side portions arepreferably sealed to one another by bonding or crimping to preventrelease of opened tow 312 and particles of SAP. The absorbent corecomposite 348, comprising the assembly of the first and second casingsheet supplies 316, 318 and the opened tow 312 and SAP 326 core, may befurther processed as it is conveyed through the assembly line forinclusion into absorbent garments 10. For example, in a preferredembodiment, the absorbent core composite 348 is severed into individualabsorbent cores 6, and the severed ends may be crimped or bonded toprevent the SAP 326 from exiting the ends.

[0124] In all cases, at least one of the first and second casing sheets316, 318 should be liquid permeable and positioned in the garment toface the wearer's body to allow the flow of fluids into the core 6. Theother casing sheet supply may optionally be liquid impermeable. Theliquid impermeability or permeability of either of the casing sheetsupplies 316, 318 may be provided by chemical or physical treatment, orby the proper selection of materials, as is known in the art. In analternative preferred embodiment, the first and second casing sheets316, 318 may both be formed from a single sheet of material that isfolded to encase the opened tow 312 and SAP 326. In such an embodiment,the structure of various parts of the system may be optionally bemodified to facilitate the manufacture of an absorbent core compositehaving a single casing sheet, as explained in more detail subsequentlyherein.

[0125] It may be desirable to apply an adhesive to one or both of thefirst and second casing sheet supplies 316, 318 prior to joining themwith the opened tow 312 or tow/SAP combination. For example, in onepreferred embodiment, an adhesive is applied to the entire width of oneor both of the casing sheet supplies 316, 318 by adhesive applicators328 before they are joined with the opened tow 312 to provide a betterbond between the casing sheets 316, 318 and the tow/SAP composite. Insuch an embodiment, the adhesive may also function to fix a portion ofthe SAP particles 326 in place. In another preferred embodiment, thesupplies of casing sheet material 316, 318 are wider than the tow/SAPcomposite, and adhesive is applied along the lateral edges of one orboth of the casing sheet supplies to join them to one another, therebysealing in the tow/SAP composite. Other uses of adhesives will beapparent to those skilled in the art based on the teachings providedherein.

[0126] A preferred adhesive for these and other embodiments is H2561Uhot melt construction adhesive, available from Ato Findley, Inc. ofWauwatosa, Wis. Other suitable adhesives, known in the art, may be usedprovided they do not excessively impair the desired properties of thecasing sheet material (as described elsewhere herein), or add excessivestiffness to the absorbent core 6. For example, other adhesives mayinclude HL-1258 by H. B. Fuller Company of St. Paul, Minn.; Findley 2031and H2587-01 by Ato Findley Inc. of Wauwatosa, Wis.; and NS34-5665 byNational Starch Co. of Bridgewater, N.J. Other adhesives that may beused include 34-578A by National Starch Co. of Bridgewater, N.J. Inanother preferred embodiment, the adhesive may be selected to impartdesired properties to the casing sheet supplies 316, 318. For example,an adhesive may be used to render one of the casing sheet supplies 316,318 fluid impervious, opaque, hydrophobic (or hydrophilic), and so onthe adhesive may also be water soluble or have other beneficialproperties. Adhesive applicators that may be used with the presentinvention include spray applicators, such as those provided by NordsonCorporation of Westlake, Ohio, or other suitable applicators, as areknown in the art.

[0127] Still referring to FIG. 3, in a preferred embodiment theabsorbent core composite 348 is assembled in four procedures that takeplace as the various parts of the assembly are pulled onto the rotatingvacuum draw roll 322. In the first step, which takes place at locationA, the first casing sheet supply 316 is drawn onto the vacuum draw roll322. In the second step, at location B, the opened tow 312 is drawn ontothe vacuum draw roll 322 to overlay the first casing sheet supply 316after being pulled out of the forming jet assembly 304. In the thirdstep, at location C, a supply of SAP 326 is deposited onto the openedtow 312 by the vibratory feeder 332, as described herein. And in thefourth step, at location D, the second casing sheet supply 318 isbrought in to overlie the first casing sheet supply 316, opened tow 312and deposited SAP. Those skilled in the art will appreciate that thesesteps may be performed using equipment other than that specificallydescribed herein, and may also be performed in various different orders,with some of the steps being rearranged, omitted or combined, or withadditional steps being performed. Such variations are generally withinthe scope of the present invention.

[0128] Also in a preferred embodiment, a lay on roll 330 is used topress the second casing sheet supply 318 against the tow/SAP compositeand the first casing sheet supply 316. The lay on roll 330 helps flattenthe core assembly and improves the edge seals between the first andsecond casing sheet supplies 316, 318. The lay on roll 330 may also beequipped to provide ultrasonic, heat, or other bonds between one or moreof the first and second casing sheets 316,318 and the tow/SAP composite.In such an embodiment, the lay on roll 330 may cooperate with the vacuumdraw roll 322 or other device to create the desired bonds. For example,portions of the lay on roll 330 may form ultrasonic horns, whilecorresponding portions of the vacuum draw roll 332 form ultrasonicanvils that, together, form an ultrasonic bond between the first andsecond casing sheet supplies 316, 318.

[0129] The superabsorbent particles preferably are provided by avibratory feeder 332, however any other suitable SAP feed device, suchas auger-type feeders and SAP sprays also may be used. The vibratoryfeeder 332 comprises a feed tray 334 that is attached to and driven by amotor 340. The motor 340 vibrates the feed tray 334, moving it back andforth in the direction of vibration V, as indicated by the double-headedarrow in FIG. 3. The feed tray 334 is supplied from above by a hopper336 by way of a flexible coupling 338 that helps isolate the hopper 336from the movement of the feed tray 334. The vibratory feeder ispreferably suspended on one or more, and most preferably three, scales342 that weigh the vibratory feeder 332 and its contents. The vibratoryfeeder 332 is preferably positioned so that none of its moving parts,particularly the motor 340 and feed tray 334 strike other parts of themachinery during operation.

[0130] The hopper 336 is preferably selected to provide consistent flowcharacteristics for a variety of superabsorbent polymers or otherparticulate and fibrous additives. In particular, it is preferred thatthe hopper 336 should flow all of its contents in a regular manner,described as “mass flow,” so that few or none of the particles becomestuck in the hopper 336, and do not experience sudden surges in the flowrate. Mass flow is present when essentially all of the material in thehopper is in motion whenever any material is withdrawn. This type offlow pattern is also described as first-in-first-out flow. In order toprovide the desired mass flow, the hopper 336 is preferably designed toavoid “bridging” (i.e., when particles become lodged in the hopper byforming a “bridge” or arch-like structure that resists flowing), and toavoid “ratholing” (i.e., when a column of particles flows through thecenter of the hopper 336, but those particles along the walls do notflow). When the hopper 336 provides mass flow, it is not necessary toprovide undesirable external forces, which may damage or redistributethe particles, to shake unmoving particles free. Mass flow may beobtained by providing the hopper 336 with relatively smooth interiorwalls and by avoiding the use of shallow flow angles within the hopper336. The design may vary depending on the particulate matter or SAP 326being held in the hopper 336, and it may be desirable to test theproperties of the material, such as the material's slip angle and angleof repose, to obtain a suitable hopper design. The design of mass flowhoppers is generally known in the art, and a skilled artisan will beable to design a suitable hopper without undue experimentation based onthe teachings provided herein.

[0131] In one embodiment, the hopper has a capacity of about 1.5 ft³ toabout 10 ft³, and more preferably about 2.25 ft³ to about 6 ft³, andmost preferably about 3 ft³. Also in a preferred embodiment, the hopper336 discharges through an outlet having a diameter of about 4 inches toabout 12 inches, and more preferably about 5 to about 9 inches, and mostpreferably about 7 inches. The hopper 336 may be supplied and refilledwith SAP using any device and method known in the art. In a preferredembodiment, the hopper 336 is filled by a screw (or “auger”) typeconveyor that moves SAP from a supply source into the hopper 336. Thedesign of such hoppers 336, conveyors and supply sources is known in theart, and a skilled artisan will be able to provide a hopper 336 for usewith the present invention without undue experimentation based on theteachings provided herein.

[0132] In a preferred embodiment, the hopper 336 is derived from aSOLIDSFLOW MODEL 5007 DRY MATERIAL FEEDER. Also in a preferredembodiment, the hopper 336 is supplied and refilled from a SOLIDSFLOWMODEL SBS BULK BAG DISCHARGE STATION using a FLEXICON flexible screw(auger) conveyor, which is controlled by a SOLIDSFLOW MODEL 1200LOSS-IN-WEIGHT CONTROLLER. All of these devices are available fromSolidsFlow Corporation of Fort Mill, S.C.

[0133] The vibratory feeder 332 may be suspended from one or more, andmost preferably three, scales 342 that measure the weight of thevibratory feeder 332 and its contents. The scales may be used tocalculate the amount of SAP 326 that is being distributed onto theopened tow 312. Such systems are commonly known as “loss-in-weight”systems, as they continuously measure the reduction in weight of thevibratory feeder 332 as its contents are being emptied. The conveyorsand supply sources that feed into the hopper 336 may also be suspendedon scales so that SAP may be added to the hopper during operation, whilestill being able to calculate the amount of SAP being deposited onto theopened tow 312. In a preferred embodiment, the loss-in-weightmeasurements of the scales 342 are used with a closed-loop feedbackcircuit to control the amount of SAP 326 that is deposited onto theopened tow 312. Such a circuit is preferably integrated into a controlsystem 320 that may control other features and operation of thevibratory feeder 332 and related devices. The scales 342 may also beused to determine when it is necessary or desirable to refill thehopper.

[0134] The scales 342 are preferably able to read to an accuracy thatallows useful determination of the amount of SAP being deposited ontothe opened tow 312. In a preferred embodiment, the scales 342 read to anaccuracy of about +/−10 grams, and more preferably of about +/−1 gram,and most preferably of about +/−0.1 gram. In a preferred embodiment, thescales 342 comprise strain gauge-type load measurement cells, such asthose available under the designation SOLIDSFLOW MODEL 1000 SCALEASSEMBLY from SolidsFlow Corporation of Fort Mill, S.C. The design,construction, and use of scales suitable for use with the presentinvention is known in the art.

[0135] A flexible coupling 338 preferably joins the hopper 336 to thefeed tray 334. The flexible coupling 338 is used pass SAP or otheradditives from the hopper 336 to the feed tray 334, while simultaneouslyisolating the hopper 336 from the vibratory movement of the feed tray334 and motor 340. The flexible coupling 338 may comprise any durableflexible material, such as canvas and other cloths, or natural orsynthetic rubbers. It is preferred that the flexible coupling does notdamp or impede the desired vibrating motion of the feed tray 334 andmotor 340, and thereby impair the ideal SAP feeding. For example, if theflexible coupling 338 is too rigid, it will reduce the ability of themotor 340 to vibrate the feed tray 334 because it will resistdeformation, effectively increasing the mass of the feed tray 334. Also,if the flexible coupling 338 is too elastically resilient, it will tendto store energy created in it when the feed tray 334 and motor 340 arevibrating, and return this stored energy in an uncontrolled manner(i.e., vibrate on its own) thereby creating additional uncontrolledvibrations in the feed tray 334 and motor 340. It also is preferred thatthe flexible coupling 338 be as light as possible so as to reduce theinertia that must be overcome by the motor 340 during operation. In apreferred embodiment, the flexible coupling 338 comprises a rubbermaterial having a diameter and shape selected to join the outlet of thehopper 336 with the inlet chute 402 of the feed tray 334.

[0136] The feed tray 334 and motor 340 preferably are suspended belowthe hopper 336 by flexible mounts 344 that allow the motor 340 and feedtray 334 to move relative to the hopper 336. The flexible mounts 344 maycomprise rods having flexible or pivoting couplings joining them, ateach end, to the hopper 336, motor 340 and feed tray 334. In a preferredembodiment, the flexible mounts 344 are designed to convey a minimalamount of vertical movement or vibration to the hopper 336, which maycause the scales 342 to read inaccurately. In such a preferredembodiment, the flexible mounts 344 may be joined to one or more of thehopper 336, motor 340 and feed tray 334 by a dry or liquid-filledelastomeric bushing or coupling. The design and selection of suchvibration- and movement-damping couplings are known in the art, and askilled artisan will be able to select or produce an appropriatecoupling system based on the teachings provided herein.

[0137] Referring now to FIG. 4, the feed tray 434 preferably comprisesan inlet chute 402 that is attached to the flexible coupling 338 toreceive SAP 326 from the hopper 336. A pan 404 extends away from theinlet chute 402 at a downward angle a to an outlet edge 406 of the feedtray 334. The pan 404 may also comprise multiple sections that descendat varying angles. The feed tray 334 preferably is covered along most ofits length to prevent disturbances of the SAP 326 or other particulateadditives. The covered portion preferably terminates at an adjustablegate 408 located near the outlet edge 406 of the feed tray 334. Theadjustable gate 408 is spaced above the pan 404 and generally dividesthe feed tray into an upstream portion from which the SAP 326 flows anda downstream portion. The adjustable gate 408 may be operated manually,or may be opened and closed by an actuating device, such as anelectromechanical, mechanical, pneumatic, or hydraulic device. Such anactuating device may optionally be controlled by a control system 320using a closed-loop feedback algorithm or open-loop algorithm. Suchactuating devices are known in the art, and a skilled artisan will beable to employ a suitable actuating device without undueexperimentation. Of course, in one embodiment the gate may be a fixedgate, rather than an adjustable gate.

[0138] In a preferred embodiment, the SAP 326 or other particulateadditive material exits the feed tray 334 at its outlet edge 406 in acurtain-like stream having a consistent flow rate across its entirewidth. Referring to FIG. 7, the active width WA of the feed tray 334 isthe width of the portion of the feed tray 334 from which the SAP 326flows (which may be affected by the use of SAP guides 410, as describedelsewhere herein), and generally corresponds to the width of the SAPflow. The active width WA may vary from one application to the next, andmay be varied during operation by using, for example actuated pivotingSAP guides 410 that move together and apart under the control of acontrol system 320. Generally, the active width WA preferably isapproximately the same width as the opened tow 312. In one embodimentthe active width WA is about 2 inches to about 12 inches, and is morepreferably about 3 inches to about 10 inches, and, in a particularlypreferred embodiment, the active width WA is as about 3.75 inches toabout 4 inches.

[0139] In other embodiments it may be desirable to vary the flow rate ofthe SAP 326 in particular areas to provide zoned absorbency. Referringnow to FIG. 15 the pan 404 may be contoured or shaped to provideconcentrated flows of SAP during operation or to otherwise control theflow of the SAP. For example, in one embodiment the pan 404 may have oneor more depressions 1502 along the outlet edge 406 that effectivelyincrease the downward angle a at the depressions 1502. In such anembodiment, the SAP 326 may tend to funnel into the depressions 1502,and those portions of the opened tow 312 that pass beneath thedepressions 1502 should receive a relatively high concentration of SAP326. In another embodiment, the pan 404 may have troughs 1504 thatextend below the adjustable gate 408, effectively increasing the heighth of the adjustable gate 408 at those points to increase the flow rateof SAP through the troughs 1504. Such troughs 1504 may extend to theoutlet edge 406 to additionally act as depressions 1502, as describedabove. Other variations in the outlet edge 406 and pan 404 geometry willbe apparent to those skilled in the art based on the teachings providedherein.

[0140] In one embodiment, the feed tray 434 may have more than one inletchute 402 so that a number of different supplies of SAP may be fed intoit. The supplies of SAP may comprise different types of SAP that areblended or isolated from one another using internal baffles and guides.In such an embodiment, for example, one type of SAP may be distributedto the lateral sides of the opened tow 312, and another type of SAP maybe distributed to the central region of the opened tow 312. Othervariations and uses of a feed tray 334 having multiple inlet chutes 402will be apparent to those skilled in the art based on the teachingsprovided herein.

[0141] SAP guides 410, comprising vertical or angled strips of material,optionally may be integrated into the feed tray 334 on either side ofthe adjustable gate 408 to serve a number of purposes. The SAP guidesare preferably attached to the pan 404, but may also be attachedelsewhere to the feed tray 334 or to other objects. In a preferredembodiment, the guides contain the lateral movement of the SAP 326 sothat it falls only in a center region of the opened tow 312. In anotherpreferred embodiment, the SAP guides 410 isolate the flow of SAP 326from turbulent airflow around the feed tray 334 to provide more even SAPdistribution. The SAP guides 410 may be proximal to the outlet edge 406,as shown in FIG. 4, or may be located elsewhere on the pan 404. The SAPguides 410 may also be used to isolate or blend different supplies ofSAP. In one embodiment, the SAP guides 410 may also comprise additionalvertically stacked layers, in addition to the pan 404, that may containseparate flows of SAP. In a preferred embodiment, the SAP guides 410 arespaced apart by about 3.75 inches to about 4 inches to provide about a3.75 inch to about 4 inch wide flow of SAP.

[0142] Referring now to FIGS. 5A and 5B, the feed tray 334 operates onthe principle that particulate solids within them, such as SAP 326, willrest at their angle of repose until disturbed by vibrations induced bythe motor 340. This principle of operation is more fully disclosed inU.S. Pat. No. 3,973,703 to Peschl, which is incorporated by referenceherein in its entirety and in a manner consistent with the presentinvention (hereafter referred to herein as “Peschl”). It should beunderstood that, although the inventors provide various theories on themodes of operation of the vibratory feeder 332, the invention is notintended to be limited to these or other modes or theories of operation.

[0143] It has been found that the flow of the SAP 326 generally may beinfluenced by the properties of the SAP, the downward angle a of the pan404, the rate of vibration of the motor 340, the trailing distance d ofthe pan 404, and the height of the adjustable gate 408. In theembodiment shown in FIG. 5A, the feed tray 334 is shown at rest, withthe SAP 326 being contained within the feed tray 334. In the embodimentof FIG. 5A, the downward angle a is greater than the angle of repose ofthe SAP 326, and so any SAP remaining along the trailing distance d ofthe pan 404 slides off the pan 404 after the motor 340 stops vibrating.The remaining SAP 326 is caught behind a bridge 502 of SAP that forms byfriction between the particles of SAP, cohesion between the SAPparticles, or both. The adjustable gate height h may be adjusted toprovide ideal SAP containment and control. Raising the adjustable gate408 generally provides a greater SAP flow rate for a given motorvibration frequency, while lowering the adjustable gate 408 generallyprovides the opposite result. The adjustable gate height h preferably isadjusted to ensure that a bridge 502 forms promptly after the motor 340stops vibrating the feed tray 334 to stop the flow of SAP 326 as quicklyas possible.

[0144] The flow rate of the SAP generally follows the vibration rate ofthe motor 340, and stops flowing almost immediately upon shut down ofthe motor 340. Generally, faster motor vibration rates provide greaterSAP flow rates and slower motor vibration rates provide a slower SAPflow rate. There is little or no appreciable time delay between changesin the motor frequency and the flow rate of the SAP 326, so thevibratory feeder 332 provides relatively accurate control of the SAPflow, especially when compared to known methods of distributing SAP ontoopened tow 312 or fluff pulp.

[0145] It should be noted that SAP remaining on the trailing distance dof the pan 404 may continue to flow at an uncontrolled rate after themotor frequency changes, but such lag time has not been found to causean appreciable detriment to the device's ability to accurately depositSAP 326 onto the opened tow 312. If a detriment is found, however, thetrailing distance d may be reduced to make the SAP flow rate follow themotor frequency variations more closely. Reducing the trailing distancemay also increase the flow rate of the SAP for a given motor frequencyand adjustable gate height h, as is explained in more detail in Peschl.In one embodiment, the trailing distance may be reduced to zero, and theoutlet edge 406 even may be within the upstream portion of the feed tray334 (i.e., the adjustable gate 408 may be located beyond the outlet edge406).

[0146] In a more preferred embodiment, shown in FIG. 5B, the downwardangle a may be less than the SAP's angle of repose and slip angle (i.e.,the angle at which the SAP 326 will slide down the surface of the pan404), so that when the feed tray 334 is at rest the SAP remaining alongthe trailing distance d stays on the pan 404. In such an embodiment, theaforementioned lag between SAP flow and motor frequency changesassociated with the SAP located in the trailing distance d may bereduced.

[0147] Referring back to FIG. 4, it has been found that the feed tray'soutlet edge 406 should be located as close as possible to the vacuumdraw roll 322. Reducing the offset distance c between the outlet edge406 and the vacuum draw roll 322 provides a number of benefits. Inparticular, minimizing the offset distance c allows the SAP to fall ontothe opened tow 312 as quickly as possible, minimizing any redistributionor diffusion of SAP 326 that may be caused during a longer fall byturbulent air flowing around the feed tray 334 and by interactionbetween the SAP particles 326. Reducing the offset distance c alsodecreases the lag time between changes in motor speed 340 and changes inthe amount of SAP 326 being distributed to the opened tow 312. In apreferred embodiment, the offset distance is about 0.25 inches to about4.00 inches, and more preferably about 0.375 inches to about 1.00 inch,and most preferably about 0.50 inches.

[0148] The minimum value for the offset distance c may be affected bymachine operating tolerances, such as to prevent contact between theopen tow 312 or the vacuum draw roll 322 and the vibrating feed tray334, or by other factors, such as the tolerances of the casing sheetsupplies 316, 318 and opened tow 312. For example, in a preferredembodiment, the offset distance c is at least about 0.50 inches to allowpassage of clumped aggregations of opened tow 312, that may be presentduring startup and during other operating conditions.

[0149] In a preferred embodiment that may be used with a variety ofSAPs, the downward angle α, as measured relative to horizontal, is about10 degrees to about 45 degrees, and more preferably about 12 degrees toabout 30 degrees, and most preferably about 15 degrees. Also in apreferred embodiment, the adjustable gate height h is about 0.10 inchesto about 1.00 inches, and more preferably about 0.125 inches to about0.75 inches, and most preferably about 0.25 inches to about 0.50 inches.Also in a preferred embodiment, the trailing distance d is about 0.25inches to about 8 inches, and more preferably about 2 to about 6 inches,and most preferably about 4 inches. Also in a preferred embodiment, theinlet chute 402 has a diameter of about 4 inches to about 12 inches, andmore preferably about 5 to about 9 inches, and most preferably about 7inches. In a preferred embodiment, the feed tray 334 may be derived froma SOLIDSFLOW MODEL 5000 DRY MATERIAL FEEDER, available from SolidsFlowCorporation of Fort Mill, S.C.

[0150] Referring now to FIGS. 6 and 7, the feed tray 334 preferably isequipped with side plates 602 that help isolate the SAP 326 and openedtow 312 from lateral airflow and may help contain the lateral movementof SAP 326 after it exits the feed tray 334. Such lateral airflow andother airflow may disturb the desired distribution of SAP onto theopened tow 312. The side plates 602 are preferably orientedapproximately parallel to the machine direction of the opened tow 312(i.e., within about 20 degrees of parallel) and sized to substantiallyreduce or block air from flowing laterally into the area beneath thefeed tray 334. Preferably, a first edge 604 of each side plate 602 islocated proximal to the vacuum draw roll 322 (or other similar drawingdevice); and a second edge 606 of each side plate 602 is locatedproximal to the forming jet assembly 304. The side plates 602 arepreferably shaped and sized so that they do not strike any other partsof the machine as they are vibrated back and forth. A third edge 608 ofeach side plate 602 preferably is adapted to conform to the secondcasing sheet supply 318 to help prevent lateral airflow from above thefeed tray from encroaching upon the supply of SAP 326. In such anembodiment, it also may be desirable for the top edge 610 of theadjustable gate 408 to be proximal to the second casing sheet supply 318to further reduce the amount of air that flows in to potentially disturbthe SAP 326. The SAP guides 410 may also have an edge 612 contoured tobe adjacent to the second casing sheet supply 318 to further inhibit thedevelopment of undesirable airflow near the SAP 326. The side plates 602preferably may be adjusted in at least the vertical direction, asindicated by the double-headed arrow in FIG. 6. In other embodiments,the side plate 602 may be attached to something other than the feed tray334, but in such embodiments, care should be taken to prevent the movingfeed tray 334 from striking the side plates 602 during operation.

[0151] Referring back to FIG. 4, the motor 340 is used to initiate andmodulate the flow of SAP 326 out of the feed tray 334. The motor 340vibrates the feed tray 334 by moving it back and forth in the directionof vibration V, as indicated by the double-headed arrow in FIG. 4. In apreferred embodiment, both the pitch p and frequency of the motor 340may be adjusted to modulate the flow of SAP 326. It has been found thatincreasing the motor's pitch p (i.e., the distance traversed by themotor during each cycle) generally increases the SAP flow rate, andvice-versa. Also, as noted before, it has been found that increasing themotor's frequency generally also increases the SAP flow rate, andvice-versa.

[0152] The effectiveness of the motor 340 and amount of control providedby the motor 340 are affected by the weight and rigidity of the feedtray 334. If the feed tray 334 is too heavy, its inertia will resist theforces imparted upon it by the motor 340, and the motor 340 may not beable to accelerate and decelerate it back and forth to create thedesired pitch p distance or frequency vibrations. If the feed tray 334is not rigid enough, it will flex as the motor 340 imparts forces on it.As the feed tray 334 flexes, it absorbs the energy that was intended tomove the feed tray 334 and does not accurately follow the path intendedby the motor 340. The energy absorbed by a flexible feed tray 334 may bereleased in the form of undesirable variations in the intended pitch pand frequency of vibration. It has been found that it is generallydesirable to make the feed tray 334 as light and as rigid as possible inorder to provide the greatest amount of control of the SAP flow.

[0153] In a preferred embodiment, the motor 340 is coupled to the feedtray 334 through a coupling 412. In order to provide accuratetransmission of the motor's vibrations to the feed tray 334, thecoupling 412 should be rigid in the vibration direction V, and thecoupling 412 preferably has a box-like shape or C-shape. Also in apreferred embodiment, the inlet chute 402, which may comprise arelatively large open space that may be susceptible to undesirableflexing, is reinforced with a structural member, such as a tubular brace414 aligned in the vibration direction V. In an embodiment in which theinlet chute has a diameter of about 7 inches it has been found that atubular brace 414 of about 1 inch diameter is suitable to reduceundesirable flexure in the inlet chute 402 without adversely affectingthe flow of SAP through the inlet chute. In other embodiments, in whichthe inlet chute 402 contains baffles or other internal flow-directing orflow-controlling structures, these structures may also serve to increasethe feed tray's rigidity, making it unnecessary to reinforce the inletchute 402.

[0154] As noted before, the motor 340 and feed tray 334 are suspendedbeneath the hopper 336 by flexible mounts 344 that allow both the motor340 and the feed tray 334 to move independently of the hopper 336. Assuch, as the motor 340 vibrates the feed tray 334 back and forth, themotor 340 itself may also move back and forth. In a preferredembodiment, the mass of the motor 340 is significantly greater than thecombined mass of the feed tray 334 and the SAP 326 contained therein,and so the movement of the motor 340 will be insignificant relative tothe movement of the feed tray 334. In such an embodiment, the motor'spitch p will be almost entirely converted into movement of the feed tray334 (as is shown in FIG. 4). If, however, the motor 340 does experiencea significant amount of movement, more of the pitch p will be convertedinto the motor's movement, and less of the pitch will result in movementof the feed tray 334. This reduction in the movement of the feed tray334 may result in less effective SAP distribution and control. If it isfound that the movement of the motor negatively affects the SAPdistribution and control, the motor's movement may be restricted, or thepitch p may be increased to increase the effective movement of the feedtray 334. Other measures may also be taken to counteract such negativeaffects. Those skilled in the art will be able to measure or calculatethe movement of the motor 340 and feed tray 334 and make accommodationsin the design of the apparatus for such movements using the teachingsprovided herein.

[0155] In a preferred embodiment, the motor 340 comprises anelectromagnetic vibrator, such as those supplied by Eriez, Corporationof Erie, Pa. as Model Number 30A, part number 3N-56743. Such a motor maybe selected to be driven by any available power source, such as a 115volt, 60 Hz power source. The motor may also require specific support ordrive hardware and software, such as an Eriez VTF signal followingcontroller board that is supported by and AB SLC 0-20 mA analog card,available from Allen-Bradley Company of Milwaukee, Wis. Other motors 340may also be used, such a rotary motor that is configured to providecyclical lateral movement or vibrations to the feed tray 334. Otheruseful motors 340 include pneumatic, magnetic, electric and hydraulicactuators, and the like, as long as they can provide the necessaryforces to vibrate the feed tray 334 at the desired pitch p andfrequency. Electromagnetic vibrators are preferred, as they typicallyprovide relatively controllable movement and consume less energy thanother devices.

[0156] In one embodiment that should be suitable for dispensing avariety of SAP materials, the motor 340 may be operated from astandstill (zero Hz) up to about 430 Hz, and more preferably up to about520 Hz, and most preferably up to about 600 Hz. In a preferredembodiment that should be suitable for dispensing a variety of SAPmaterials, the frequency is approximately constant, and the flow rate ofthe particulate matter is controlled by modulating the motor's pitch. Insuch a preferred embodiment, the motor frequency is about 60 Hz, and thepitch p of the motor variable between about 0.01 inches to about 0.125inches, and more preferably about 0.02 inches to about 0.10 inches, andmost preferably about 0.04 inches to about 0.08 inches. Such adjustmentsmay be obtained, for example, by varying the voltage of the motorbetween about 0 and about 90 volts.

[0157] Such a vibratory feeder 332 may be adapted to provide a highvolume of SAP flow, and may be used at relatively high manufacturingline speeds. It is anticipated that a vibratory feeder producedaccording to a preferred embodiment of the present invention may be usedwith an assembly line producing diapers at a rate in excess of 600products per minute. The vibratory feeder 332 preferably can feedsuperabsorbent polymer or other additives at a rate of about 10,000grams per minute (g/min) to about 20,000 g/min, and more preferably at arate of about 12,500 g/min to about 17,500 g/min, and most preferably ata rate of about 15,000 g/min. In a preferred embodiment, the hopper 336is fed by a screw-type conveyor or other conveyor that has a capacity tomaintain a useful level of SAP 326 in the vibratory feeder 332. Theconveyor may have a feed rate that is less than the maximum feed rate ofthe vibratory feeder 332, so long as the average feed rate of thevibratory feeder 332 does not exceed the average feed rate of theconveyor.

[0158] Superabsorbent polymers and other particulate additives can berelatively expensive, and so it is often desirable to minimize theamount of SAP that is placed in the core and to “zone” such additivesonly where they are most beneficial for the final product. Such zoningis also particularly beneficial in tow-based absorbent cores because thelack of fluff pulp in such cores may reduce the overall wickingcapability of the core, making it more important to place the SAP closerto the location where fluid is likely to strike the garment. In apreferred embodiment, the motor 340 is controlled by a control system320 to provide a desirable distribution of SAP 326 into the opened tow312. In one preferred embodiment, such a control system 320 may be usedto operate the motor 320 to deposit a steady stream of SAP 326 onto theopened tow 312 to provide a uniform opened tow/SAP mixture in theabsorbent cores that are ultimately formed by the process. In anotherpreferred embodiment, the control system may cyclically increase anddecrease the pitch p and/or frequency of the motor 340 to deposit apulsating supply of SAP 326 to the opened tow 312, thereby providing theabsorbent cores with targeted concentrations of SAP that provide thegarment 10 with zoned absorbency. Preferably, the control system 320uses a closed-loop feedback method that considers various factors indetermining how much SAP to distribute at any given moment.

[0159] In a preferred embodiment, the control system 320 is providedwith information about how fast the assembly line is running by using,for example, a tachometer 346 on the vacuum draw roll 322 or by anyother suitable line speed measuring device (See FIG. 3). By integratingsuch a line speed measuring device into the control system 320, thecontrol system 320 may be programmed to increase or decrease the pitch por frequency of the motor 340 to vary the SAP flow rate as the productmanufacturing rate changes, thereby providing all of the products withthe proper amount of SAP, regardless of the assembly line speed. Such acapability provides a lower rate of product rejection duringtransitional phases, thereby improving the overall efficiency of themanufacturing process.

[0160] In another preferred embodiment, the output of the scales 342 isintegrated into the control system 320. By considering the weight of theSAP being distributed, as measured by the scales 342, the control system320 may programmed to modulate the motor 340 to accurately distributeSAP at the desired flow rate. In such an embodiment, the control system320 may also accommodate for deviations in the flow characteristics ofthe SAP particles to continue to provide an even flow, such as byincreasing the vibration rate if it is found that the SAP is not flowingas rapidly as expected, and vice-versa. Such deviations may be caused bytypical variations in the shape, size, humidity, density, or otherfeatures of the SAP, or may be caused when a different SAP product isused in a machine that was originally set up for another type of SAP orset up for a SAP provided by a different supplier.

[0161] A closed-loop feedback control system 320 may also be programmedto stop distributing SAP in the event that a fault is detected in theprocessing line. For example, if a fault detection circuit tied into thecontrol system 320 determines that one or more products will bedefective upon completion, the flow of SAP may be stopped so that thedefective products will not receive SAP. In such an embodiment, it maybe desirable to produce the absorbent cores of the garments as late aspossible in the manufacturing process in order to detect as many defectsas possible before preparing the absorbent core 6 for each product.

[0162] In one embodiment, a SAP concentration detection device 350 (FIG.3) may be integrated into the control system 320 to provide furtherdetection and control capabilities to the control system 320. Theconcentration detection device 350 may be located to measure the amountand/or location of SAP in the assembled absorbent core composite 348. Ifthe amount of location of the SAP is not present as desired, theconcentration detection device 350 may signal this to the control system320 so that appropriate corrections in the SAP feed rate may be made.Those skilled in the art are capable of designing or utilizing asuitable SAP concentration detection device 350 using the guidelinesprovided herein.

[0163] The flow rate of the SAP may also be controlled by a controldevice 320 by actively adjusting the height h of the adjustable gate 408during operation. As noted before, the adjustable gate 408 may be raisedand lowered during operation to increase and decrease, respectively, theflow rate of the SAP 326. Such adjustments may also be made to provide acyclically fluctuating amount of SAP to the opened tow 312 to createtargeted regions of relatively high SAP concentration for zonedabsorbency. In such an embodiment, the control device 320 may operatethe adjustable gate 408 in conjunction with the scales 342, tachometer346, concentration detection device 350, or other sensors to provideclosed-loop feedback control of the SAP flow. A suitable actuationdevice for cyclically raising and lowering the adjustable gate 408preferably does not cause excessive vibrations or other movements thatmay cause the scales 342 to read inaccurately.

[0164] Referring now to FIG. 8, it has been found that a “combiningdrum”-type vacuum draw roll 800 may be advantageously used inconjunction with vibratory feeders 332, such as those described herein,or, alternatively, with other SAP feed devices and methods, such asthose that are known in the art. The combining drum 800 is characterizedin that several or all of the parts that eventually form the absorbentcore 6 of the garment 10 are assembled in a continuous motion around allor part of the combining drum's circumference. In a preferredembodiment, the combining drum 800 combines the first casing sheetsupply 316, opened tow 312, SAP 326 and second casing sheet supply 318(i.e., various constituent parts of the core composite 348, which may,of course, include other parts) in a substantially continuous operationas they are conveyed by the combining drum 800. Each of the parts may beconveyed to the combining drum 800 separately and then joined togetherinto an integrated structure, or alternatively, some of the parts may bejoined to one another prior to contact with the combining drum 800. Forexample, an additional layer 20 may be affixed to either side of one orboth of the first and second casing sheet supplies 316, 318 before thesupply is provided to the combining drum 800.

[0165] As noted before, a preferred combining process has been generallydescribed elsewhere herein with reference to Locations A, B, C and D ofFIG. 3. The operation of the combining drum 800 described herein isrelatively simple compared to many known core-forming apparatus, and maybe adapted to operate at high line speeds. For example, it isanticipated that the combining drum 800 may be adapted to operate withan assembly line producing in excess of 600 diapers per minute.

[0166] In a preferred embodiment the combining drum 800 has a generallycylindrical surface 802 with a vacuum surface 804 forming acircumferential belt on the cylindrical surface 802. The vacuum surface804 comprises one or more holes 806 through which a vacuum is applied tothe various parts of the core composite 348. The holes 806 in the vacuumsurface 804 may be formed by any means known in the art, such asdrilling, machining, casting and so on. In a preferred embodiment, theholes 806 have a diameter of about 0.0625 inches to about 0.75 inches,and more preferably of about 0.125 inches to about 0.625 inches, andmost preferably of about 0.25 inches to about 0.50 inches. Also in apreferred embodiment, the holes may be spaced from one another by acenter-to-center distance of about 0.10 inches to about 1.00 inch. Theholes may be spaced in a rectilinear array, as staggered rows, or in anyother pattern that conveys the desired amount of vacuum. The vacuumsurface 804 also may comprise any other relatively rigid foraminousstructure, such as one or more mesh screens or removable perforatedplates that are affixed to openings in the cylindrical surface 802. In apreferred embodiment, the combining drum 800 may also comprise landingareas 808 on either side of the vacuum surface 804 which may be treatedto enhance their ability to grip the first and second casing layersupplies 316, 318. A vacuum is applied to the combining drum 800 througha vacuum port 810.

[0167] Referring now to FIG. 9, there is shown a sectional view of thevacuum surface 804 region of a combining drum 800 as is appears justafter combining the first casing sheet supply 316, opened tow 312, SAP326 and second casing sheet supply 318 into an integrated core composite348. The width W₁ of the vacuum surface 804 (as measured in a directionparallel to the rotational axis of the combining drum 800) preferablycorresponds approximately to the width of the opened tow 312 and to thewidth of the portion of the feed tray 334 from which SAP 326 isprovided. The first and second casing sheet supplies 316, 318 arepreferably wider than the opened tow 312, and their excess width islocated in side areas 902 that overlie the landing areas 808. The firstand second casing sheet supplies 316, 318 preferably are joined to oneanother in their side areas 902 by adhesive bonding, other methodsdescribed elsewhere herein or by other methods known in the art. Asnoted elsewhere, a lay on roll 330 may be used to help join the firstand second casing sheet supplies 316, 318 by use of pressure, crimpingnodules, and the like.

[0168] In a preferred embodiment, the vacuum surface 804 is recessed inthe cylindrical surface by a depth y of less than about 0.50 inches, andmore preferably by less than about 0.10 inches, and most preferably byabout 0.030 inches. It has been found that having a slight increase inthe diameter of the combining drum 800 on either side of the vacuumsurface 804 (i.e., a recessed vacuum surface 804) helps keep the firstcasing sheet supply 316 stretched across the combining drum 800 duringoperation.

[0169] The vacuum surface width W₁ may be selected to provide certainbenefits to the garment into which the core composite 348 is beingintegrated. In one embodiment, the core composite may be integrated intothe garment in a flat state, in which case it may be desirable to makethe vacuum surface width W₁ and the width of the opened tow 312 equal tothe desired width of the garment's absorbent core 6. However, the corecomposite 348 may be stretched, folded, or otherwise resized duringmanufacture, in which case the vacuum surface width W₁ should becorrespondingly adjusted. In a preferred embodiment, the core composite348 is folded at least once before being integrated into the garment.Folded absorbent cores have been discussed in more detail elsewhereherein. In a preferred embodiment, the vacuum surface width W₁ is about1.75 inches to about 12 inches, and more preferably about 2.75 inches toabout 10 inches, and most preferably about 3.75 inches. In order toreduce SAP loss during core formation, the vacuum surface width ispreferably slightly narrower (about 0.10 inches on either side) than thewidth of the supply of opened tow 312 to promote a slight inwardmigration of SAP away from the side areas 902.

[0170] As noted before, it has been a continuing challenge to providethe desired distribution of SAP within the absorbent cores 6 ofabsorbent garments 10. It has been found that a combining drum 800 asdescribed herein may be beneficially used to help provide such desiredSAP distributions. Cellulose acetate opened tow 312 and other types oflow density fibrous opened tow structures allow a relatively largeamount of air to pass through them compared to conventional fluff pulpmaterials, and the location of the SAP 326 may be effectively controlledby modulating the amount and position of the vacuum applied to theSAP/opened tow mixture. It has been found that the distribution of theSAP can be more easily controlled with tow/SAP cores than with fluff/SAPcores. As air passes through the opened tow 312 into the vacuum itconveys the SAP 326 through the fibrous structure, and the SAP particles326 generally tend to concentrate more densely at areas having a highvacuum. Also, as the vacuum is increased, the SAP particles 326generally move closer to the surface of the opened tow 312 that isadjacent the combining drum 800. The degree to which the SAP migratestowards the high vacuum areas may also be affected by the duration oftime that the vacuum is applied to the SAP 326. The vacuum also helpsprevent SAP 326 from escaping out of the opened tow 312 duringmanufacturing. It has been found that a desirable mixture of SAP 326within the opened tow 312 and reduced SAP loss may be produced using avacuum of about 2.50 inches of water to about 20 inches of water, andmore preferably of about 3.75 inches of water to about 12.5 inches ofwater, and most preferably of about 5.0 inches of water. The vacuum maybe pre-set or may be manually or actively controlled by a control system320 using an open-or closed-loop feedback system.

[0171] In addition to being useful for providing a homogeneousdispersion of SAP 326 in the opened tow 312, a combing drum 800 asdescribed herein may also be used to accomplish various other desirableSAP distribution patterns. In one embodiment, the vacuum level may bemodulated to provide a desirable depth of SAP penetration throughout theopened tow 312 or only in discrete areas of the opened tow 312. In otherembodiments, the combining drum 800 may be adapted to provide machinedirection (MD) and cross-machine direction (CD) zoning of the SAPparticles 326 that provide the garment 10 with zoned absorbency. Themachine direction is the direction in which a part or assembly movesduring processing, and the cross-machine direction is perpendicular tothe MD. The machine direction generally corresponds to the longitudinaldimension 100 of the fully-assembled garment 10 (see FIG. 1), and thecross machine direction corresponds to the lateral dimension 102 of thegarment, however other relationships may also be used and are within thescope of the present invention.

[0172] Referring now to FIG. 10, regions of high SAP concentration, andthus greater absorbency, may be provided in the MD and CD by making thevacuum surface 804 with particularly designed target regions 1002 thatconvey a greater amount of vacuum to portions of the opened tow 312.Such target regions 1002 may have larger holes and/or a greaterconcentration of holes in those areas where a greater concentration ofSAP 326 is desired. The larger amount of open space provided in suchregions will allow a greater amount of airflow into the vacuum, and thuscause a greater amount of SAP to migrate to those areas. For example, inthe embodiment of FIG. 10, the region 1004 has a greater concentrationof larger holes, which should provide a SAP concentration in the portionof the core composite 384 adjacent region 1004. The particular patternof SAP concentration may be adjusted by making each of the targetregions 1002 from a removable plate 1006 having the desired holepattern. Substitute plates 1006 may be easily machined to providedifferent hole patterns and zoned absorbency patterns.

[0173] In another embodiment, shown in FIG. 11, the vacuum surface 804may be separated into discrete target regions 1102, which may havevarying widths, to provide zones of high and low MD and CD SAPconcentrations.

[0174] In an embodiment in which the combining drum 800 has targetregions 1002, 1102 for providing zoned absorbency, the combining drumdiameter D₁ should be selected so that the corresponding parts of eachtarget regions 1002, 1102 are spaced from one another around thecircumference of the combining drum 800 by a distance corresponding tothe absorbent core length X₁. By using such a spacing, each targetregion 1002, 1102 will create a targeted zone of SAP that will beproperly located in each absorbent core 6 that is cut from the corecomposite 348.

[0175] It should be understood that by providing a distance betweencorresponding parts of each target region 1002, 1102 that isapproximately equal to a core length X₁, the circumference of thecombining drum 800 will be sized to equal a whole number multiple of thecore length X₁. At a minimum, the circumference can equal one corelength X₁, but in such an embodiment, the various parts of the corecomposite 348 will be in contact with the vacuum for relatively littletime, which may lead to inadequate SAP distribution or other formingproblems. Smaller diameter drums may also be subject to greatervibration. These problems may become exacerbated when the vacuum drum800 is used with higher speed assembly lines. Problems may also be existwith larger drum diameters. For example, the manufacturing tolerancesfor a larger diameter drum may be less precise. In addition, as the sizeof the drum increases the amount of startup waste may increase,particularly if a greater amount of vacuum is required for the largerdrum, leading to longer vacuum stabilization times. Larger drums thatrequire greater amounts of vacuum also may require more power to producethe necessary vacuum. It will be understood that these considerationsalso apply to embodiments of the invention in which the combining drum800 does not have target regions 1002, 1102, such as in the embodimentdepicted in FIG. 8.

[0176] It is preferred, therefore, that the drum diameter D₁ be selectedso that the drum's circumference is large enough that the parts of thecore composite 348 are in contact with the vacuum long enough toproperly distribute the SAP without excessive vibrations, but smallenough to provide the required precision and a minimal amount of startupwaste. It has been found that in a preferred embodiment, the diameter D₁is selected so that the circumference is equal to between three andseven core lengths X₁. In a preferred embodiment, the combining drum 800(whether it has target regions 1002, 1102 or not) has a diameter D₁ ofabout 6 inches to about 28 inches, and more preferably of about 9 inchesto about 20 inches, and most preferably of about 12 inches. In thisembodiment, the number of wasted cores caused by vacuum hysteresis orother startup-related issues has been found to be about 5 products perstartup, as compared to up to about 50 products per startup withconventional core forming processes. It has also been found thatproviding the necessary vacuum to such a combining drum 800 requiresabout 10 horsepower to 20 horsepower, whereas conventional core formingsystems require up to about 400 horsepower, and so a significant powersavings is provided.

[0177] Referring now to FIGS. 12 through 14, a preferred embodiment ofthe combining drum is shown in which the combining drum 800 may beconfigured to apply a vacuum to the parts of the core composite 348 onlythrough a portion of the drum's rotation. The combining drum 800 of apreferred embodiment comprises an outer drum 1202 that is positioned torotate about a fixed inner drum 1204 by, for example, being affixed toan axle 1208 that passes through rotary bearings 1210 in the inner drum1204. Such bearings 1210 may be equipped to reduce or prevent theleakage of the vacuum through them. A vacuum is applied to the space1206 inside the inner drum by a vacuum port 810. The vacuum is conveyedto the outer drum's vacuum surface 804 by way of one or more passages1212 through the inner drum 1204 that are preferably located subadjacentthe path of the vacuum surface 804 of the outer drum 1202 to maximizethe strength of the vacuum applied through the vacuum surface 804. Itwill be understood by those skilled in the art that the inner drum 1204may be replaced by any vacuum chamber having one or more passages 1212that convey a vacuum to a location subadjacent all or part of the vacuumsurface 804.

[0178] Only those portions of the vacuum surface 804 that areimmediately adjacent the passages 1212 receive a vacuum, so the durationand location of the vacuum's application may be modified by changing thesize, number, or location of the passages 1212. Referring specificallyto FIG. 13, the passages 1212 may be positioned through an arc of theinner drum 1204 that defines a vacuum zone Θ_(V). The leading edge ofthe vacuum zone 1302 is preferably located proximal to the point atwhich the first casing sheet supply 316 contacts the combining drum,which is designated as Location A in FIG. 3. The trailing edge of thevacuum zone 1304 is preferably located beyond (as the drum rotates) thepoint at which the second casing sheet supply 318 contacts the combiningdrum 800, which is designated as Location D in FIG. 3. Referring now toFIG. 14, it can be seen that those portions of the vacuum surface 804that are not adjacent the passages 1212 are effectively cut off from thepull of the vacuum. After the core composite 348 passes the trailingedge of the vacuum zone 1304 and reaches this blocked-off area it isreleased from the vacuum's hold and conveyed to other parts of theassembly line.

[0179] The size of the vacuum zone Θ_(V) may vary depending on where thevarious parts are desired to be assembled to form the core composite348. In a preferred embodiment, the vacuum zone Θ_(V) is about 45degrees to about 180 degrees, and more preferably is about 90 degrees toabout 160 degrees, and most preferably is about 140 degrees.

[0180] Various devices may be employed with the combining drum 800 tomodulate the location and amount of vacuum applied to the core composite348. In one embodiment, shown in FIG. 13, internal sleeves 1306 or othervalving mechanisms may be used to adjust the points at which the vacuumzone Θ_(V) begins and ends. In another embodiment, shown in FIG. 12,other internal sleeves 1214 or other valving mechanisms may be used tonarrow or widen the width of the vacuum zone Θ_(V), thereby effectivelynarrowing and widening the width W₁ of the vacuum surface 804. In stillanother embodiment, an internal sleeve or other valving mechanism may beused to reduce the vacuum level within all or part of the inner drum1204. Any of such sleeves and valving mechanisms may be actuated by acontrol system 320 under the guidance of an open- or closed-loopfeedback system. Greater or lesser amounts of vacuum may also be appliedin discrete portions of the vacuum zone Θ_(V). Other designs will beobvious to one skilled in the art based on the teachings providedherein.

[0181] A combining drum 800, as described herein, may be used with anySAP feeding device that deposits SAP onto opened tow or other fibrousmaterials. The embodiments of the combining drum 800 described hereinhave been found to be particularly useful when used in conjunction withthe vibratory feeder 332 as described herein.

[0182] The present invention offers several advantages over previous SAPdepositing systems. In particular, the vibratory feeder 332 providesimproved control over the volume and placement of the SAP 326 in thefiber, preferably the opened tow 312, allowing greater control over theSAP distribution (and zoned absorbency) during transitional phases, suchas during machine startup, stopping and other speed changes, leading tofewer rejected products during such times. In addition, the vibratoryfeeder 332 and combining drum 800 provide improved SAP penetration intothe fiber, preferably the opened tow 312 or other core material, and animproved ability to selectively position the SAP to provide desirablezoned absorbency. The vibrator feeder 332 and combining drum 800 alsoprovide easier operation, as the various features of each device may beintegrated into a control system 320. Stull further, the vibratoryfeeder 332 and combining drum 800 are relatively simple and reliabledevices that require little maintenance or cleaning, thereby reducingthe operating cost of the machine. Another advantage of the vibratoryfeeder 332 and combining drum 800 is that they may be operated at highline speeds without detriment to the product quality. Other benefitswill be apparent to those skilled in the art based on the teachingsprovided herein.

[0183] In another embodiment, the present invention provides anapparatus and method for forming absorbent structures that have a singlecasing sheet. Single-sheet absorbent cores are manufactured with asingle casing sheet (rather than multiple casing sheets, as describedpreviously herein) that is wrapped around all or part of the absorbentcore material. The use of a single casing sheet has been found toprovide manufacturing and economic advantages over using multiple casingsheets because the single sheet does not require slitting and rerouting,and can be bonded to itself at a single seam, rather than multiple seamsas in the case of multiple casing sheets. As with multiple sheet cores,such single-sheet absorbent structures may be used in any absorbentproduct, including garments, such as diapers and pull-on pants,catamenial devices, absorbent wipes or sheets, and so on. Although it isknown to manufacture conventional fluff pulp/SAP absorbent cores havinga single casing sheet, it has been found that known methods andapparatuses for forming single-sheet core structures are notparticularly useful for forming single-sheet core structures made usingtow-based absorbent cores.

[0184] Referring now to FIGS. 16A and 16B, embodiments of single-sheetabsorbent structures that may be manufactured using the presentinvention are shown in cross-section. In FIG. 16A, the absorbentstructure is shown as it might appear when installed in an exemplaryabsorbent product, in FIG. 16B the structure is shown with the rest ofthe absorbent product omitted for clarity. The single-sheet absorbentstructure comprises a tow-based absorbent core 1606 wrapped in a singlecasing sheet 1618. As can be seen in FIGS. 16A and 16B, the casing sheet1618 initially may be wider than the absorbent core 1606, and thenfolded over the core 1606 to fully encase it. The embodiment of FIG. 16Ademonstrates a tri-fold design, in which the casing sheet 1618 is foldedat two locations to form three sheet portions. FIG. 16B demonstrates abi-fold design, in which the casing sheet 1618 is folded at one locationto form two sheet portions. The two ends 1618 a, 1618 b of the casingsheet 1618 may overlap one another so that the inside of one end 1618 babuts the outside of the other end 1618 a, as shown in FIG. 16A, or maybe pinch-seamed so that the two ends 1618 a, 1618 b abut one another ontheir interior sides, as shown in FIG. 16B. The ends 1618 a, 1618 b ofthe casing sheet 1618 also may abut one another without any substantialoverlap, or may be attached and some or all of the overlapping portionsremoved before final assembly into a product. Also, in any case, theseam may be located on the top, bottom or sides of the absorbent core1606, and may be unbonded or bonded (such as shown by bond 1622) usingany known or later-developed bonding technique. Various usefulcompositions of the tow-based absorbent core 1606 and casing sheet 1618have been described in more detail previously herein. In a preferredembodiment, the casing sheet 1618 comprises a sheet of tissue.

[0185] Other features of the exemplary garment 1600 of FIG. 16A includea fluid pervious topsheet 1602 and fluid impervious backsheet 1604.Garment 1600 may also have fluid pervious or impervious wastecontainment flaps 1612, which may contain elastic members 1614, and legelastics 1608 adjacent the leg openings 1628 a, 1628 b to help controlleakage. An additional layer 1620, comprising a wicking layer or thelike, may also be provided in the garment 1600, and may be locatedinside the casing sheet 1618, outside the casing sheet 1618, or betweenthe overlapped ends 1618 a, 1618 b of the casing sheet 1618. Usefulmaterials and constructions for these and other components of exemplarygarment 1600 have been described in more detail elsewhere herein.

[0186] It has been found that the present invention can be adapted toprovide a continuous supply of single-sheet, tow-based absorbent corestructures in an economical and effective manner. In the presentinvention, a vacuum draw roll, such as those described elsewhere herein,is used in conjunction with angled surfaces and other folding devices tocombine the tow, SAP and casing sheet into a fully folded continuoussupply of absorbent core composite material. From this continuoussupply, a series of single-sheet absorbent structures may be cut to formindividual absorbent cores, which may be integrated into any type ofabsorbent article or device or used on their own. Various embodiments ofthe present invention are now described with reference to FIGS. 17-29.

[0187] In one embodiment of the present invention, shown in FIG. 17, avacuum draw roll 1708, is operated in conjunction with a tapered breakdrum 1714 and folders 1716 to form and fold a single-sheet corecomposite supply. In this embodiment, the materials required to form theabsorbent structure are provided to the apparatus by a tow supplymechanism 1702, a particulate matter supply mechanism 1704, and a casingsheet supply mechanism 1706. The tow supply mechanism 1702 may compriseany tow conveying device that provides a supply of tow, such has rollersor the like, and preferably comprises a tow forming jet, as describedpreviously herein. The tow 1703 may be any suitable tow, as describedabove, for forming an absorbent structure, and preferably is a celluloseacetate tow that is opened prior to or while being supplied to theapparatus of the present invention. The particulate matter supplymechanism 1704 provides SAP and/or other additives in particulate form(which may include powders, grains, flakes, microfibers and the like) tothe apparatus, and may comprise any conventional feed device, or morepreferably, a vibratory feeder, such as those described herein. Thecasing sheet supply mechanism 1706 is shown as a single roller, but maycomprise any sheet conveying device or devices, such as rollers, feedrolls, festoons, and the like, as are well known in the art, that arecapable of providing a casing sheet supply 1707 (preferably a sheet oftissue) in a controlled manner to the apparatus.

[0188] With respect to the vacuum draw roll 1708, the casing sheetsupply mechanism 1706, the particulate matter supply mechanism 1704 andthe tow supply mechanism 1702, the embodiment of FIG. 17 may operate inmuch the same manner as the embodiments of these components describedelsewhere herein, such as with reference to FIG. 3. More specifically,the vacuum draw roll 1708 rotates about a first axis 1710 and pulls theopened tow 1703 out of the tow supply mechanism 1702 and joins it withthe casing sheet supply 1707. The particulate matter supply mechanism1704 is positioned to deposit SAP 1705 or other particulate additives tothe opened tow before it is combined with the casing sheet supply 1707.In addition, a first adhesive applicator 1712 may be positioned to sprayadhesive on the portion of the casing sheet supply 1707 that contactsthe tow 1703 to provide adhesion between the tow 1703 and the casingsheet supply 1707, and to adhere the SAP 1705 in place. Of course, thesevarious components can be repositioned in various ways, and it isanticipated; for example, that the invention may be configured such thatthe particulate matter supply mechanism 1704 deposits the SAP 1705directly onto the casing sheet supply 1707 or such that the firstadhesive applicator 1712 sprays adhesive directly onto the tow 1703.

[0189] Like the other vacuum draw rolls and combining drums describedelsewhere herein, the vacuum drum has a foraminous center surface (seeFIGS. 8 and 24) that applies a vacuum to the tow 1703 and casing sheetsupply 1707. It has been found that relatively little vacuum isnecessary, and a vacuum of about 1 to 2 inches of water, and preferably1.5 inches of water is adequate for high speed core forming operations.The foraminous center surface may be shaped to accommodate and conveythe tow 1703, and may be flat, rounded, angled, recessed and so on. In apreferred embodiment the foraminous center surface has a recessedportion, such as is shown in FIGS. 9 and 27. Other features andembodiments of the vacuum draw roll 1708 are described in more detailelsewhere herein.

[0190] In the embodiment of FIG. 17, the casing sheet supply 1707, tow1703 and SAP 1705 (or other particulate additives) are combined on thevacuum draw roll 1708 into an unfolded open core composite supply 1718that is open on the side that faces the vacuum draw roll 1708. For thepurposes of this disclosure, the term “open core composite supply” meansany composite structure having a tow material on one side and a casingsheet material on the other side, wherein the casing sheet material doesnot fully enclose the tow material (thus leaving the composite structure“open”). It should be noted that in this embodiment the tow 1703 is theonly material between the SAP 1705 and the foraminous surface and vacuumof the vacuum draw roll 1708. It has been found that the tow 1703 hasthe unexpected ability to act as a filter that provides sufficientresistance to impede the flow of the SAP 1705 and prevent the loss ofany substantial amount of SAP 1705 into the vacuum. After being formed,the open core composite supply 1718 preferably is transferred to avacuum conveyor 1726 for further processing.

[0191] It has been found that a significant amount of static electricitycan accumulate on the tow 1703 during the opening process when a towforming jet is used. This static electricity can generate enoughattraction between the vacuum draw roll 1714 and the open core compositesupply 1718 to cause undesirable clinging that can create irregularitiesin the operating path of the open core composite supply 1718 and inhibitthe speed at which the apparatus can operate. In order to reduce oreliminate this static charge accumulation, water may be introduced inthe tow forming jet and/or on the vacuum draw roll 1714 to help reducestatic accumulation and facilitate the release of the open corecomposite supply from the vacuum draw roll 1714.

[0192] In other embodiments, an additional layer of material (notshown), such as a wicking layer or acquisition layer may be placed onthe vacuum draw roll 1708 either before or after the tow 1703 and/orcasing sheet supply 1717 is applied to the vacuum draw roll 1708. Inthese embodiments, the absorbent core composite supply may be formedwith an integral layer 1620 being incorporated directly into thestructure.

[0193] The casing sheet supply 1707, SAP 1705 and tow 1703 are formedinto a substantially flat and folded supply of core composite materialin a process shown representatively by FIGS. 18A-18C. FIGS. 18A-18C arecross-sectional drawings of the core composite materials shown atreference lines 4-4, 5-5 and 6-6 in FIG. 17, respectively, with themachinery omitted for clarity. In the first step, the various materialsare combined together to form an open core composite supply 1718. In theembodiment of FIG. 17, the open core composite supply 1718 is providedin a substantially flat configuration, as shown in FIG. 18A. Next, asshown in FIG. 18B, the open core composite supply 1718 is folded so thatit has one or more obtuse angles Θ_(o) in it. Finally, thepartially-folded open core composite supply 1718 is fully folded so thatit is substantially flat, as shown in FIG. 18C. Although the embodimentshown in FIGS. 18A-18C depicts a tri-fold design, it will be appreciatedthat by using a single obtuse angle Θ_(o), a bi-fold design may be made.In other embodiments, such as those described subsequently herein withreference to FIGS. 21 to 27, the various steps described above,particularly the first and second steps, may be combined to improveefficiency, reduce apparatus size or obtain other benefits.

[0194] In the embodiment of FIGS. 18A-18C, The casing sheet supply 1707preferably is wider than the tow supply 1703 so that the ends of thecasing sheet supply can be folded over and joined to one another. Inthis embodiment, the casing sheet comprises three regions: a centerregion R₁ and first and second lateral regions R₂, R₃. The center regionR₁ is located approximately along the centerline of the casing sheetsupply 1707, while the first and second lateral regions R₂, R₃ arelocated on either side of the center region R₁. The edges of the centerregion R₁ are defined by the locations at which the obtuse angles Θ_(o)are made. It is also anticipated that the center region R₁ can be offsetto one side, and one or both of the lateral regions R₂, R₃ can be foldedto cover the tow to form the core composite as a bi-fold design (inwhich only one side region is folded) or a tri-fold design having anoffset seam.

[0195] The first adhesive applicator 1712, if used, applies adhesive1802 continuously or intermittently to the center region to adhere thetow to the casing sheet supply 1707 and hold the SAP in place. Theadhesive 1802 may be applied in lines, swirls, bands or in any otheruseful pattern. Adhesive preferably is not applied in the lateralregions R₂, R₃ during the initial assembly stages because such adhesivemight adhere to the vacuum draw roll 1708 or other machinery andinterfere with manufacturing. As noted elsewhere herein, the type andamount of adhesive should be selected to minimize any detriment to theabsorbing capability of the core composite, and standard constructionadhesive may applied to the casing sheet supply 1707 by a standard meltblown spray adhesive applicator. The selection of adhesives, whetherhydrophobic or hydrophilic, and different types of applicators will beunderstood by those of ordinary skill in the art. A suitable selectionof adhesives and applicators will be readily apparent without undueexperimentation.

[0196] In a preferred embodiment, the obtuse angles Θ_(o) are formed inthe casing sheet supply 1707 outboard of the tow 1703, as shown in theFigures. It is also anticipated, however, that it may be useful to formthe obtuse angles Θ_(o) at locations slightly inboard of the edges ofthe tow 1703 so that the tow 1703 has thicker edges. In a bi-folddesign, the tow 1703 may also be folded along its centerline to form adouble-thickness structure.

[0197] The obtuse angles Θ_(o) may be formed in the open core compositesupply 1718 by breaking the open core composite supply 1718 using one ormore angled surfaces. In the embodiment of FIG. 17, the open corecomposite supply 1718 is conveyed over a tapered break drum 1714 havingan integral pair of angled surfaces 1720. The tapered break drum isshown in more detail in FIG. 19. As shown in FIG. 19, the tapered breakdrum 1714 comprises a center surface 1902 (which may be cylindrical,rounded, recessed or otherwise shaped or textured) and two angledsurfaces 1720. The two angled surfaces 1720 extend from a respectiveedge 1904 of the center surface 1902 and taper (preferably in a conicalfashion) to have a smaller diameter as they proceed away from the centersurface 1902. The angle of the taper, is selected to impart the desiredobtuse angles Θ_(o) in the open core composite supply 1718. In order tominimize friction on the open core composite supply 1718, the taperedbreak drum 1714 preferably rotates about an axis 1906 so that thesurface speed of the tapered break drum 1714 approximately matches thatof the open core composite supply 1718, and is preferably designed tohave a low rotational inertia to allow the drum to quickly respond tochanges in operating speed. The tapered break drum 1714 is positioned inthe assembly line such that it tends to create tension in the centerregion R₁ of the open core composite supply 1718, as shown, for example,in FIG. 17. When the tapered break drum 1714 is thus positioned, theside regions R₁, R₂, which are not under as much tension as the centerregion R₁, tend to follow the path of least resistance by following thecontours of the angled surfaces 1720, thereby forming the obtuse anglesΘ_(o).

[0198] In another embodiment shown in FIG. 20, the angled surfaces mayinstead comprise rollers 2004 or fixed guides that are placed at anglesadjacent to an untapered break drum 2002. In this embodiment, the breakdrum 2002 applies tension to the center region R₁ of the open corecomposite supply 1718, and the rollers 2004 impart the desired obtuseangles ΘO in the side regions R₁, R₂ of the open core composite supply1718.

[0199] The size of the obtuse angles Θ_(o) preferably are selected toincrease the speed at which the open core composite supply 1718 can befolded by the folders 1716. This angle may depend on the type of folders1716 that are employed. It is also anticipated that in a tri-fold designthe obtuse angles Θ_(o) may be different for each side of the open corecomposite supply. In a preferred embodiment, the obtuse angles Θ_(o) arebetween about 130 degrees and about 175 degrees. In a more preferredembodiment, the obtuse angles Θ_(o) are between about 140 degrees andabout 165 degrees. In an even more preferred embodiment, the obtuseangles Θ_(o) are about 154 degrees.

[0200] After the obtuse angle Θ_(o) or angles are made in the open corecomposite supply 1718, it is conveyed to one or more folders 1716 thatfold the composite into a substantially flat folded core compositesupply 1724. The folders 1716 may comprise any known folding equipment,but preferably comprise a set of folding boards that maintainsubstantially equal web tensions across the cross-direction of thetissue sheet (i.e., in the direction perpendicular to the machinedirection. Ideally, the folding boards prevent unwanted wrinkling orbuckling in the tissue sheet.

[0201] A second adhesive applicator 1722 may, in some embodiments, beprovided to apply adhesive to the center or side regions R₁, R₂, R₃during the folding process to hold the casing sheet supply 1707 in placeonce the folded core composite supply 1724 is formed. Such adhesive maybe applied on either side of the casing sheet supply 1707, and may alsobe applied on the tow 1703. It will be appreciated that the design andlocation of the second adhesive applicator 1722 should be selected sothat it is operatively associated with the folder 1716 such that itapplies adhesive to the proper surfaces either before, during or afterthe folding operation performed by the folder 1716. The relativepositioning of these devices, and other manners in which the secondadhesive applicator 1722 may be operatively associated with the folder1716 will be readily understood by those of ordinary in the art. In apreferred embodiment, the second adhesive applicator 1722 comprises aslot-coater that applies construction adhesive to seal the casing sheetsupply 1707 after it is has been folded. The slot-coater preferablycomprises a blade-like device that slips between the overlappingportions of the casing sheet supply 1707 and applies adhesive to one orboth of the facing portions of the folded, but as yet unbonded, casingsheet supply 1707. Of course, the second adhesive applicator 1722 mayalso comprise any conventional adhesive applicator, such as a sprayadhesive applicator or conventional slot adhesive applicator positionedprior to or above the folder 1716 that applies adhesive before thecasing sheet supply 1707 is fully folded. After the adhesive is appliedby the second adhesive applicator 1722, the folded core composite supply1724 may be may be pressed in a pinch roller or in a debulker (notshown) to help seal the adhesive. Alternatively, or in addition to thesecond adhesive applicator 1722, other bonding devices or methods may beused. For example, in a bi-fold design, an edge sealer may be employedafter the second adhesive applicator to attach the edges of the casingsheet supply, as shown in FIG. 16B. In still other embodiments, thecasing sheet supply 1707 may not be sealed at this point, and mayinstead be held in its closed position by contact with other parts of agarment or other article into which the folded core composite supply1724 is integrated.

[0202] Referring now to FIG. 21, in another embodiment of the invention,the angled surfaces may be integrated into the vacuum draw roll, therebymaking the apparatus more compact and removing the necessity ofproviding a separate break roll or other devices between the vacuum drawroll and the folders 1716. In this embodiment the vacuum draw roll is atapered vacuum draw roll 2102 that comprises one or more angled surfaces2104. The tapered vacuum draw roll 2102 simultaneously forms the opencore composite supply 1718 and creates the obtuse angles Θ_(o) in theopen core composite supply 1718. A vacuum conveyor 2108 then transportsthe open core composite supply 1718 to the one or more folding devices1716 where it is folded into a folded core composite supply 1724. In avariation of the embodiment of FIG. 21, shown in FIG. 22, the vacuumconveyor 2108 may comprise an arcuate portion 2110 that wraps partiallyaround the tapered vacuum draw roll 2102. It is believed that in thisembodiment the presence of the arcuate portion of the conveyor may helpretain the SAP 1705 or other particulate matter or additives in positionduring the forming operation.

[0203] A tapered or stepped lay-on roll 2106 also may be used inconjunction with the embodiment of FIG. 21 to help conform the casingsheet supply 1707 to the angled surfaces 2104 of the tapered vacuum drawroll 2102. An example of a tapered lay-on roll 2106 is shown in moredetail in FIG. 23. In the example of FIG. 23, the tapered lay-on rollhas two tapered surfaces 2302 that abut the angled surfaces 2104 of thevacuum draw roll during use, and may optionally have a center surface3204 having an appropriate shape (preferably cylindrical) to generallyabut the center surface of the tapered vacuum draw roll 2102. In otherembodiments, the tapered surfaces may be replaced by one or morecylindrical or disc-like surfaces.

[0204] An embodiment of a tapered vacuum draw roll of the presentinvention is now described in detail with reference to FIGS. 24-27. FIG.24 is an isometric view of a tapered vacuum draw roll 2402 showing theangled surfaces 2404 (one of which is visible) and foraminous centersurface 2406. The angled surfaces 2404 and foraminous center surface2406 are disposed on a rotatable drum 2412 that is positioned outside aninner structure 2408. The inner structure 2408 contains one or morevacuum passages to convey a vacuum to the foraminous center surface2406. The angled surfaces 2404 preferably comprise tapered surfaces,preferably shaped as conic sections, such as those described withreference to the tapered break drum 1714 of FIGS. 17 and 19. Also shownin FIG. 24 is a vacuum port 2410 that may be connected to a vacuumsource. Of course, it will be appreciated that in embodiments of theinvention in which a bi-fold core design is produced, there may only beone angled surface 2404, and the foraminous center surface 2406 may notbe located in the center of the rotatable drum. Also in a bi-folddesign, the center surface may be peaked in the middle to break the opencore composite supply 1718 along or near its centerline.

[0205] Referring now to FIGS. 25 and 26, the internal structure oftapered vacuum draw roll 2402 is described. As noted before, the taperedvacuum draw roll 2402 comprises a rotatable outer drum 2412 disposedaround an inner structure 2408. For clarity, in FIG. 25 the outer drum2412 is shown cut away at about the middle of the foraminous centersurface 2406 and the passages through the foraminous center surface 2406are omitted in both FIGS. 25 and 26. In this embodiment, the innerstructure 2408 comprises a vacuum chamber 2414 to which a vacuum isprovided. The inner structure 2408 also has one or more vacuum passages2418 that place the vacuum chamber 2414 in fluid communication with theunderside of the foraminous center surface. As best seen in FIG. 26,there may be a space 2420 between the foraminous center surface 2406 andthe outer surface of the inner structure 2408. In order to prevent thevacuum from being applied the entire circumference of the foraminouscenter surface 2406, a pair of vacuum blocks 2422 are placed in thespace 2420 to inhibit the fluid communication of the vacuum. As shown inFIG. 25, the placement of the vacuum blocks 2422 dictates the size ofthe vacuum zone Θ_(V) in which vacuum is applied to the foraminouscenter surface 2406.

[0206] In a preferred embodiment, the tapered vacuum draw roll 2402 (orany other draw roll) may be further equipped with a pressurized airblow-off port to help remove the open core composite supply 1718 forfurther processing. In such an embodiment, the inner structure 2408 mayfurther comprise a pressurized chamber 2416 to which pressurized air isprovided. The pressurized air in the pressurized chamber 2416 is placedin fluid communication with the foraminous center surface 2406 to expelthe open core composite supply 1718 after it reaches the trailing edgeof the vacuum zone (iv. Preferably, this is accomplished by providingthe vacuum block located at the trailing edge of the vacuum zone Θ_(V)with an air blow-off passage 2424 that is in fluid communication withthe pressurized chamber 2416. As the outer drum 2412 rotates, theforaminous center surface 2406 passes over the blow-off passage 2424,and the pressurized air therein is forced out of the foraminous centersurface 2406, creating a force to release the open core composite supply1718.

[0207] The foraminous center surface 2406 may be any suitable surfacehaving holes or slots to pass a vacuum therethrough, and preferably issimilar to the vacuum surface 804 described previously herein withreference to FIG. 8. Referring now to FIG. 27, in a preferredembodiment, the foraminous center surface comprises three vacuumregions: a central vacuum region Z₁ and first and second lateral vacuumregions Z₂, Z₃. The central vacuum region Z₁ preferably is approximatelythe same width as the supply of tow material 1703, and is recessed toaccommodate the tow 1707 to some degree as it is being conveyed. Thelateral vacuum regions Z₂, Z₃, are disposed in either side of thecentral vacuum region Z₁, and contact the casing sheet supply 1707during operation. The purpose of the lateral vacuum regions Z₂, Z₃ is tofirmly hold the casing sheet supply 1707 to form a seal that inhibitsthe lateral escape of SAP 1705 or other additives during operation, andto improve the grip on the tow 1703 and casing sheet supply 1707 that iscreated in the central vacuum region Z₁.

[0208] In many of the embodiments described previously herein (such asthe embodiments described with reference to FIGS. 17, 21 and 22), thecasing sheet supply 1707 is conveyed along a portion of its path by thevacuum draw roll 1708, 2102 in such a manner that the casing sheetsupply 1707 wraps around a substantial portion of the vacuum draw roll1708, 2102. However, in other embodiments, the various devices describedherein can be arranged in configurations in which a vacuum draw rolldeposits tow onto a casing sheet supply that is conveyed without beingwrapped around a portion of the vacuum draw roll 2808. Variousembodiments having this configuration are now described with referenceto FIGS. 28 and 29.

[0209] Referring to FIG. 28, in one embodiment of the invention a casingsheet supply may be provided by a substantially linear conveyor 2826(preferably a vacuum conveyor), while tow 2803 is provided by a towsupply mechanism 2802 and particulate matter such as SAP 2805 isprovided by a particulate matter supply mechanism 2804. As the casingsheet supply 2807 is conveyed along the conveyor 2826, a first adhesiveapplicator 2812 applies adhesive to all or part of one side of thecasing sheet supply 2807. Next, SAP 2805 is applied, and then the tow2803 is deposited onto the casing sheet supply 2807 by a vacuum drawroll 2808 to form an open core composite supply 2818. The open corecomposite supply 2818 is then conveyed to a folder 2816 that folds itinto a substantially flat, folded core composite supply 2824.

[0210] The first adhesive applicator 2812 applies adhesive to hold theSAP in place and adhere the tow 2803 to the casing sheet supply 2807. Asecond adhesive applicator 2822 may also be used with the embodiment ofFIG. 28 to apply adhesive to either the tow 2703 or casing sheet supply2807 to hold the folded portions of the casing sheet supply 2807 inplace after it is formed into the folded core composite supply 2824. Inanother embodiment, the second adhesive applicator 2822 may be omittedif the first adhesive applicator 2812 is adapted to apply adhesive tothe portions of the casing sheet supply 2807, such as the lateralregions R₂, R₃, that will eventually be folded over to hold the foldedcore composite supply 2824 together. In an embodiment in which the firstadhesive applicator 2812 is used to apply adhesive to the lateralregions R₁, R₂ of the casing sheet supply, the vacuum draw roll 2808should be positioned so that it does not contact the portions of thecasing sheet supply 2807 that have adhesive applied to it in order toavoid accumulations of adhesive on the machinery. Of course othersealing devices, such as ultrasonic sealers, also may be used to form abond to hold the folded core composite supply 2824 together.

[0211] Embodiments in which the casing sheet supply 2807 is not conveyedaround the vacuum draw roll 2808 provide the advantage that theapparatus can be reconfigured relatively easily to modify or supplementthe assembly process. For example, as shown in FIG. 29, a third adhesiveapplicator 2813 may be included between the particulate matter supplymechanism 2804 and the vacuum draw roll 2808 to provide another layer ofadhesive to hold the SAP 2805 in place and/or to adhere the tow 2803 tothe casing sheet supply 2807. In such an embodiment, the first adhesiveapplicator 2812 may optionally be omitted.

[0212]FIG. 29 also demonstrates other features that may be used with anyembodiment of the invention. For example, a second tow supply mechanism2802′ may be used in conjunction with the original tow supply mechanism2802 to provide a second supply of tow 2803′ and thereby create amulti-component or multi-layered tow. In such an embodiment the secondsupply of tow 2803′ may be placed under, above, or next to the originalsupply of tow 2803. Also shown in FIG. 29 are a second vacuum draw roll2828 and a fourth adhesive applicator 2834 that may be used to attach anadditional supply of tow 2832 to the folded core composite supply 2824.The additional supply of tow 2832 may be used, for example, as anacquisition layer or as a transfer layer, or may be infused with anadditional supply of SAP (not shown) to act as an additional absorbentlayer.

[0213]FIG. 29 also demonstrates an embossing roll 2836 that may be usedin conjunction with the invention to emboss the casing sheet supply2807. The pattern of the embossing roll 2836 may be selected to formwells, microwells or grooves in the surface of the casing sheet supply2807. The SAP 2805 deposited on the casing sheet supply 2807 mayconcentrate in these wells or grooves, thereby creating zones of greateror lesser absorbency in the completed core composite supply 2824. Thesezones can subsequently be positioned into absorbent garments to providetargeted regions of high absorbency. The embossing provided by theembossing roll 2836 also may add loft or a more desirable texture to thestructure of the finished absorbent garment or provide other benefits.

[0214] Although FIGS. 28 and 29 and the discussion thereof describe thecasing sheet supply 2807 as being conveyed in a substantially linearfashion by conveyor 2826, it is also envisioned that conveyor 2826 mayhave a non-linear path, such as the conveyor 1726 in FIG. 17, with thevacuum draw roll 2808 being located at the point at which conveyor 2826is inverted or elsewhere. All such variations are within the scope ofthe present invention.

[0215] Although the tow supply mechanisms described thus far (i.e.,items 1702, 2802, 2802′ and 2830) have generally depicted tow formingjets, it will be understood by those of ordinary skill in the art thatthe tow supply mechanisms may also comprise any other type oftow-forming or tow-supplying device. Indeed, there is no requirementthat the tow be opened or otherwise conditioned “on the fly” during themanufacturing process. Instead, in other embodiments of the inventionthe tow may be substantially fully prepared in a separate manufacturingoperation, and supplied to the present invention as a roll good. As usedherein, “roll good” refers to any pre-made supply of material thatrequires little or no further substantive processing as it is suppliedto the present invention. A roll good preferably is provided in rollform, but also may be provided as sheets, as a folded supply, as acontinuous or discontinuous supply, or in any other suitable manner, aswill be apparent to those of ordinary skill in the art.

[0216]FIG. 30 depicts an apparatus similar to that of FIG. 29, exceptthat the tow supply mechanisms comprise various types of roll good towsupply mechanisms. As shown in FIG. 30, a first roll good tow supply3003 that forms the absorbent core 2824 may be provided as a continuoussupply from a wound reel 3002 of roll good tow material. A conventionaltissue unwinding mechanism or other suitable device may be used tocontrol the feed rate of the first roll good tow supply 3003. Variousrollers 3009 may be used to convey the first roll good tow supply 3003and press it to the casing sheet supply 2807. A second roll good towsupply 3032 also may be supplied to overlie the folded core compositesupply 2824 to act as an acquisition layer, transfer layer or the like.In the embodiment of FIG. 30, the second roll good tow supply 3032 issevered into discrete pieces 3032′ that are spaced apart and placed ontothe folded core composite supply 2824 using, for example, a conventionalvacuum transfer roll and cutting knife assembly 3028. Of course, thesecond roll good tow supply 3032 may be provided by any other suitabledevice, and need not be provided as discontinuous pieces.

[0217] Other embodiments, uses, and advantages of the invention will beapparent to those skilled in the art from consideration of thespecification and practice of the invention disclosed herein.Furthermore, the present invention may be used in combination with anysuitable prior art apparatus or methods, and any description herein ofdrawbacks or limitations of the prior art are not to be understood aslimiting the scope of the present invention to necessarily exclude theinclusion of such prior art apparatus or methods with the presentinvention. For example, it is envisioned that a second tissue layer orother casing layer may be used with the present invention to overlie theabsorbent core to provide additional tensile strength or fluid handlingcharacteristics. The specification should be considered exemplary only,and the scope of the invention is accordingly intended to be limitedonly by the following claims and equivalents thereof.

We claim:
 1. An apparatus for forming absorbent structures having a single casing sheet, the apparatus comprising: a tow supply mechanism for providing tow material; a particulate matter supply mechanism for providing particulate matter; a casing sheet supply mechanism for providing casing sheet material; a vacuum draw roll comprising a foraminous center surface, the foraminous center surface having a width defined by a first edge and a second edge and being rotatable about a first axis, the vacuum draw roll being positioned to receive the tow material, the particulate matter and the casing sheet material to form a open core composite supply; one or more angled surfaces positioned to create one or more obtuse angles in the open core composite supply; and, one or more folders to further fold the one or more obtuse angles in the open core composite supply to form a folded core composite supply.
 2. The apparatus of claim 1, wherein the tow material comprises cellulose acetate tow.
 3. The apparatus of claim 1, wherein the tow material comprises a roll good.
 4. The apparatus of claim 1, wherein the particulate matter comprises superabsorbent particles.
 5. The apparatus of claim 1, wherein the casing sheet material comprises tissue.
 6. The apparatus of claim 1, wherein the particulate matter supply mechanism is a vibratory feeder.
 7. The apparatus of claim 1, where in the tow supply mechanism is a tow forming jet.
 8. The apparatus of claim 1, wherein: the casing sheet material comprises a center region and first and second side regions located on opposite sides of the center region, the first side region extending from a first side of the center region to a first edge of the casing sheet material, and the second side region extending from a second side of the center region to a second edge of the casing sheet material; the casing sheet material is wider than the tow material; the tow material is positioned adjacent to the center region of the casing sheet material in the open core composite supply; and, the one or more angled surfaces are positioned to create a first obtuse angle proximal to the first side of the center region, and a second obtuse angle proximal to the second side of the center region.
 9. The apparatus of claim 8, further comprising a first adhesive applicator positioned before the vacuum draw roll to apply adhesive to the center region of the casing sheet material.
 10. The apparatus of claim 8, further comprising a second adhesive applicator operatively associated with the one or more folders and positioned to apply adhesive to at least one of the first and second side regions.
 11. The apparatus of claim 1, wherein the one or more angled surfaces are operatively associated with the vacuum draw roll.
 12. The apparatus of claim 11, wherein the one or more angled surfaces comprise first and second tapering surfaces, each of the first and second tapering surfaces extending from a respective edge of the foraminous center surface and tapering inward from the center surface towards the first axis.
 13. The apparatus of claim 1, further comprising a break drum positioned between the vacuum draw roll and the one or more folders, the break drum being rotatable about a second axis and comprising a center surface, the center surface having a width defined by a third edge and a fourth edge.
 14. The apparatus of claim 13, wherein the one or more angled surfaces are operatively associated with the break drum.
 15. The apparatus of claim 14, wherein the one or more angled surfaces comprise first and second tapering surfaces, each of the first and second tapering surfaces extending from a respective edge of the center surface and tapering inward from the center surface towards the second axis.
 16. The apparatus of claim 1, further comprising an open core composite supply conveyor, the open core composite supply conveyor being positioned to convey the open core composite supply from the vacuum draw roll to the one or more folders.
 17. The apparatus of claim 16, wherein the open core composite supply conveyor comprises an arcuate region substantially adjacent to a sector of the vacuum draw roll.
 18. The apparatus of claim 1, wherein the vacuum draw roll further comprises: a rotatable outer drum, wherein the foraminous center surface is disposed on the rotatable outer drum; and an inner structure disposed at least partially within the rotatable outer drum and comprising a vacuum chamber, the vacuum chamber having one or more vacuum passages forming a vacuum zone subadjacent at least a portion of the foraminous center surface.
 19. The apparatus of claim 18, wherein the one or more angled surfaces comprise first and second tapering surfaces, each of the first and second tapering surfaces being disposed on the rotatable outer drum and extending from a respective edge of the foraminous center surface and tapering inward from the center surface towards the first axis.
 20. The apparatus of claim 18, wherein the vacuum zone comprises a leading edge relative to a direction of rotation of the rotatable outer drum and a trailing edge relative to a direction of rotation of the rotatable outer drum, and the inner structure further comprises a positive air blow-off port located proximal to the trailing edge.
 21. The apparatus of claim 18, wherein the foraminous center surface comprises a central vacuum region and first and second lateral vacuum regions, the first lateral vacuum region being located between the central vacuum region and the first edge of the foraminous center surface, and the second lateral vacuum region being located between the central vacuum region and the second edge of the foraminous center surface.
 22. The apparatus of claim 21, wherein the central vacuum region is recessed.
 23. The apparatus of claim 21, wherein the tow material has an average width approximately equal to or less than a width of the central vacuum region, and the central vacuum region is positioned to receive substantially the entire width of the tow material.
 24. The apparatus of claim 23, wherein the first and second lateral vacuum regions are positioned to apply a vacuum to the casing sheet material.
 25. A method for preparing absorbent structures having a single casing sheet, the method comprising: providing tow material; providing particulate matter; providing casing sheet material; forming an open core composite supply by combining the tow material, the particulate matter and the casing sheet material on a vacuum draw roll comprising a foraminous center surface, the foraminous center surface having a width defined by a first edge and a second edge and being rotatable about a first axis; creating one or more obtuse angles in the open core composite supply using one or more angled surfaces; and, forming a folded core composite supply by folding flat the one or more obtuse angles in the open core composite supply.
 26. The method of claim 25, wherein providing tow material comprises providing cellulose acetate tow.
 27. The method of claim 25, wherein providing tow material comprises providing roll good tow material.
 28. The apparatus of claim 25, wherein providing particulate matter comprises providing superabsorbent particles.
 29. The method of claim 25, wherein providing casing sheet material comprises providing tissue.
 30. The method of claim 25, wherein: providing casing sheet material comprises providing casing sheet material comprising a center region and first and second side regions located on opposite sides of the center region, the first side region extending from a first side of the center region to a first edge of the casing sheet material, and the second side region extending from a second side of the center region to a second edge of the casing sheet material; providing tow material comprises providing tow material having a width narrower than a width of the casing sheet material; forming the open core composite supply further comprises positioning the tow material adjacent to the center region of the casing sheet material; and, creating one or more obtuse angles in the open core composite supply further comprises creating a first obtuse angles proximal to the first side of the center region, and a second obtuse angle proximal to the second side of the center region.
 31. The method of claim 30, further comprising applying adhesive to the center region before forming the open core composite supply.
 32. The method of claim 30, further comprising applying adhesive to at least one of the first and second side regions before forming the folded core composite supply.
 33. The method of claim 25, wherein forming an open core composite supply and creating one or more obtuse angles are performed simultaneously.
 34. An apparatus for forming absorbent structures having a single casing sheet, the apparatus comprising: a casing sheet supply mechanism for providing casing sheet material; a tow supply mechanism for providing tow material; a particulate matter supply mechanism for providing particulate matter, the particulate matter supply mechanism being positioned to deposit the particulate matter onto the casing sheet material; a vacuum draw roll comprising a foraminous center surface, the foraminous center surface having a width defined by a first edge and a second edge and being rotatable about a first axis, the vacuum draw roll being positioned after the particulate matter supply mechanism to deposit the tow material onto the casing sheet material to form a open core composite supply; and, one or more folders to fold the open core composite supply into a folded core composite supply.
 35. The apparatus of claim 34, wherein the tow material comprises cellulose acetate tow.
 36. The apparatus of claim 34, wherein the tow material comprises roll good tow material.
 37. The apparatus of claim 34, wherein the particulate matter comprises superabsorbent particles.
 38. The apparatus of claim 34, wherein the casing sheet material comprises tissue.
 39. The apparatus of claim 34, wherein the particulate matter supply mechanism is a vibratory feeder.
 40. The apparatus of claim 34, where in the tow supply mechanism is a tow forming jet.
 41. The apparatus of claim 34, wherein: the casing sheet material comprises a center region and first and second side regions located on opposite sides of the center region, the first side region extending from a first side of the center region to a first edge of the casing sheet material, and the second side region extending from a second side of the center region to a second edge of the casing sheet material; the casing sheet material is wider than the tow material; and, the tow material is positioned adjacent to the center region of the casing sheet material in the open core composite supply.
 42. The apparatus of claim 41, further comprising a first adhesive applicator positioned before the vacuum draw roll to apply adhesive to the center region of the casing sheet material.
 43. The apparatus of claim 41, further comprising a second adhesive applicator operatively associated with the one or more folders and positioned to apply adhesive to at least one of the first and second side regions.
 44. The apparatus of claim 34, wherein the casing sheet supply mechanism comprises a vacuum conveyor, the vacuum conveyor being positioned to convey the casing sheet supply to the one or more folders.
 45. The apparatus of claim 34, wherein the vacuum draw roll further comprises: a rotatable outer drum, wherein the foraminous center surface is disposed on the rotatable outer drum; and an inner structure disposed at least partially within the rotatable outer drum and comprising a vacuum chamber, the vacuum chamber having one or more vacuum passages forming a vacuum zone subadjacent at least a portion of the foraminous center surface.
 46. The apparatus of claim 45, wherein the vacuum zone comprises a leading edge relative to a direction of rotation of the rotatable outer drum and a trailing edge relative to a direction of rotation of the rotatable outer drum, and the inner structure further comprises a positive air blow-off port located proximal to the trailing edge. 